THE 


FORMATION  OF  POISONS 


BY 


MICRO-ORGANISMS. 


A  BIOLOGICAL  STUDY  OF  THE  GERM  THEORY  OF  DISEASE. 


BY 


G.  V.  BLACK,  M.D.,  D.D.S. 
ii 


4 

PHILADELPHIA: 

P.   BLAKISTON,   SON   &   CO., 

No.  1012  WALNUT  STREET. 

1884. 


"B-fe 


Entered  according  to  Act  of  Congress,  in  the  year  1884,  by 

G.  V.  BLACK,  M.D., 
In  the  Office  of  the  Librarian  of  Congress,  at  Washington,  D.  C. 


PRESS  OF  WM.  F.  FELL  &  Co., 

1220-24  Sansom  Street, 

Philadelphia. 


PREFACE. 

The  historical  portion  of  this  volume  has  been  condensed 
from  notes  made  from  time  to  time  in  the  study  of  the 
subject.  With  the  view  of  making  it  as  short  as  possible, 
I  have  given  only  those  experiments  and  observations  that 
seemed  important  to  a  proper  understanding  of  the  subject, 
avoiding  all  but  the  most  necessary  details;  aiming  at  the 
same  time  to  preserve  all  that  will  be  of  real  advantage  to  the 
general  student.  Many  familiar  names  will  be  missed,  for 
the  reason  that  many  have  written,  and  some  of  them  very 
well  indeed,  who  have  developed  no  distinctive  fact  or 
thought  that  is  of  service  in  the  farther  progress  of  the  sub- 
ject. When  we  come  to  analyze  any  such  subject,  most  men 
are  surprised  to  find  how  few  have  been  instrumental  in  the 
development  of  the  real  basic  facts  on  which  our  knowledge 
of  it  rests.  Therefore,  if  we  can  properly  estimate  the  import 
of  the  matter  presented,  the  history  of  the  development  of 
any  such  subject  may  be  briefly  written.  Whether  or  not  I 
have  determined  wisely,  the  intelligent  reader  must  judge. 

The  second  part  was  written  because  I  had  something  to 
say  that  I  thought  ought  to  be  said  at  the  present  time.  The 
men  who  have  been  most  instrumental  in  the  development  of 
this  subject  have  given  us  little  else  than  the  experimental 
facts.  These  will  satisfy  the  minds  of  but  very  few.  Most 
of  us  appreciate  any  subject  more  if  we  understand  why  these 
things  are  so.  It  is  this  why  that  I  have  sought  to  supply. 
This  I  leave  for  intelligent  discussion  to  sift,  and  separate  the 
good  grains  from  the  chaff. 

G.  V.  BLACK,   M.  D.,  D.  D.  S. 

JACKSONVILLE,  June  2d,  1884. 

iii 


TABLE  OF  CONTENTS. 


PAGE 

Preface iii 


FIKST  PART. 

FIRST  LECTURE. 

Introduction — First  Traces — Incentives  to  the  Study — First  Definite 
Announcement  of  the  Germ  Theory — Phlogiston — Zymosis — 
Jenner—  Fermentation  Hypothesis — Vaccine — Beginning  of  the 
Nineteenth  Century— Early  Discoveries — Astier— Schwan — Lie- 
big's  Views — Difficulties — Schroeder's  Discoveries — Schroeder's 
Conclusions — Pasteur  and  his  Work — Needham  and  Spallanzani 
—Pasteur's  Plan  of  Work 11  to  34 

SECOND  LECTURE. 

Bastian  and  his  Work — Archebiosis — Logical  Sequence — Difficulties — 
Modes  of  Propagation  of  Micro-organisms — Utilizing  Discoveries 
— Lister's  Antiseptic  Surgery — Nature  of  the  Evidence— Direct 
Examinations  for  Micro-organisms — Evidence  Unsatisfactory — 
Miasm  and  Contagion — Miasmatic  Contagion — Infection  Experi- 
ments— Discussions  by  Important  Men 35  to  56 

THIRD   LECTURE. 

Beale's  Work — The  Amoeboid  Theory  of  Contagion — Pasteur — The 
Bacillus  Anthracis— Koch  and  his  Work— Aniline  Staining — Dry 
Slide  Cultivations — Infection  Experiments — Pathogenic  Micro- 
organisms now  certainly  Demonstrated — What  is  Necessary  for 
the  Demonstration  of  a  Pathogenic  Micro-organism — The  Evi- 
dence that  Pathogenic  Micro-organisms  are  Different  from 
ordinary  Bacteria — Spores  and  Habits  of  Micro-organisms — 

Summary 57  to  76 

V 


VI  .  TABLE   OF   CONTENTS. 

SECOND  PAKT. 

FOURTH   LECTURE. 

Production  of  Poisons  by  Micro-organisms — Propositions — Necessity 
for  a  Physiological  Study  of  the  Subject— Digestion  and  Absorp- 
tion— Propositions — Primary  Digestion — Absorption — Nutritive 
Digestion— Soluble  Ferments — Digestion  by  the  Yeast  Plant- 
Mr.  Lister's  Experiments — Digestion  by  Bacteria — Digestion  by 
the  Higher  Plants— Sach's  Experiments— Sprouting  of  Seeds — 
Diastase— Nutrition 79  to  95 

FIFTH  LECTURE. 

The  Yeast  Plant— Cellular  Digestion  in  the  Higher  Animals — Re- 
sorptive  Digestion — Resorption  of  the  Roots  of  the  Milk  Teeth — 
Digestion  of  Blood  Clot — Digestion  of  Animal  Ligatures — Diges- 
tion of  Sponge  —  Necrosed  Bone  —  Pathological  Formation  of 
Soluble  Ferments — Relation  of  Soluble  Ferments  to  Living  Tis- 
sues— Parasites 96  to  110 

SIXTH  LECTURE. 

Waste  Products — Life  as  a  Force — Law  of  the  Formation  of  Waste 
Products — The  Nature  of  Waste  Products — Waste  Products  of 
the  Higher  Animals  ;  of  the  Higher  Plants  ;  of  Bacteria— Alka- 
loids  Ill  to  128 

SEVENTH  LECTURE. 

Poisons  Developed  by  Micro-organisms  —  Farther  Investigation 
Needed — Physiological  Changes  in  Micro-organisms — Manner 
of  Action — Inflammations  and  Pus  Formation — Blood  Dis- 
eases   129  to  146 

APPENDIX. 

Dental  Caries;  its  Relation  to  the  Germ  Theory  of  Disease 149  to  169 


PART  FIRST. 


ACKNOWLEDGMENT. 

This  volume  contains  a  series  of  lectures,  delivered  before 
the  students  of  the  Chicago  College  of  Dental  Surgery  and  a 
number  of  practitioners  who  were  ticketed  especially  for  this 
course.  The  Lectures  now  appear  in  their  present  form 
through  the  co-operation  and  kindly  assistance  of  the  Officers 
and  Faculty  of  that  Institution,  to  all  of  whom  I  gratefully 
acknowledge  myself  indebted  for  many  favors. 

THE  AUTHOR. 


A  STUDY 

OF   THE 


GERM  THEORY  OF  DISEASE. 


HISTORICAL. 


INTRODUCTION. 

In  presenting  an  historical  sketch  of  the  Germ  Theory  of 
Disease,  it  will  be  my  effort  to  review  briefly  the  ideas,  con- 
troversies and  experiments,  that  have  gradually  led  up  to 
our  present  knowledge  concerning  it.  At  present  I  know  of 
no  single  treatise  on  this  subject  from  which  those  who  have 
not  followed  its  now  extensive  literature  can  gain  a  clear 
view  of  it,  obtain  a  just  conception  of  its  magnitude,  of  the 
labor  that  has  been  bestowed  upon  it,  or  of  its  immense  im- 
portance. The  history  of  this  subject  in  its  completeness, 
would  be  a  history  of  the  efforts  of  men  to  stay  the  ravages 
of  epidemic  and  contagious  diseases ;  a  history  of  the  efforts 
of  men  to  understand  the  causes  of  plagues  and  pestilences ; 
a  history  of  the  efforts  of  men  to  see  farther,  and  still  farther, 
into  the  secret  causes  which  produce  sickness  and  diminish 
the  longevity  of  the  race.  I  cannot,  however,  give  more 
than  a  brief  synopsis  of  the  principal  thought,  experiment 
and  discussion,  bearing  most  directly  upon,  and  finally  lead- 
ing to  the  adoption  of  present  theories.  The  literature  of 
2  11 


12  THE   GERM   THEORY   OF   DISEASE. 

the  subject  is  DOW  quite  extensive,  and  is,  for  the  most  part, 
scattered  through  works  upon  disease  in  general,  more  es- 
pecially works  on  surgery.  Very  few  books  were  written 
especially  on  this  branch  of  medicine  until  quite  recently ; 
and  these  generally  dealt  with  some  particular  phase  of  the 
subject,  or  with  the  very  recent  experimentation,  giving  little 
or  no  account  of  preceding  inquiries.  Therefore  it  is  very 
difficult  for  one  who  takes  up  the  subject  now  to  gain  a 
comprehensive  view  of  it  as  a  whole.  It  will  be  my  object 
to  supply  such  a  view  in  a  short  and  concise  recital  of  the 
thought,  experiment  and  discussion,  that  has  been  most  eifect- 
ive  in  leading  to  our  present  knowledge,  and  most  essential 
to  an  understanding  of  the  work  now  being  done  in  this 
field. 

FIRST  TRACES. 

For  many  centuries  these  ideas  consisted  in  vague  con- 
jectures, arrived  at  from  the  study  of  contagion — an  undefined 
something  that  could  pass  from  the  sick  to  the  well,  and  cause 
disease.  We  find  that  Ulysses  (Homer's  Odyssy,  Book  XXII), 
used  sulphurous  acid  to  destroy  the  odor  and  toxic  products 
of  decomposition. 

Early  in  the  history  of  Greece  we  find  that  men  had 
learned  that  certain  localities  were  unhealthy.  Their  notion 
seemed  to  be  that  something  obnoxious  to  health  was  being 
generated  at  these  places;  and  we  find  them  acting  with 
judgment  in  regard  to  the  location  of  their  hospitals  and 
important  buildings.  The  physicians  of  antiquity  observed 
that,  in  epidemic  diseases  the  then  existing  theories  were  in- 
sufficient. They  recognized  that  there  was  something  extra- 
ordinary to  deal  with.  They  spoke  of  a  "  constitutio  pestilens  " 
and  of  a  "genus  epidemicus,"  but  as  to  the  nature  of  this 
constitution  of  disease  they  had  few  clear  ideas. 

Diodorus  found  an  explanation  of  the  cause  of  the  Athenian 


INCENTIVES   TO   THE   STUDY.  13 

Plague  in  the  circumstance  that  "  a  great  multitude  of  people 
from  all  quarters  streamed  into  the  city,  and  being  cramped 
for  room,  breathed  corrupted  air."  Decomposing  filth,  social 
squalor,  bad  weather,  etc.,  were  regarded  as  causes  of  disease, 
by  both  physicians  and  laymen. 

INCENTIVES  TO  THE  STUDY. 

When  we  turn  our  attention  to  the  contagious  diseases,  to 
the  great  plagues  of  past  times,  and  watch  the  progress  of 
thought  in  regard  to  them,  the  absence  of  knowledge  of  the 
means  of  staying  their  progress,  the  utter  helplessness  of  the 
people  in  times  of  pestilence,  seems  simply  terrible.  Without 
a  knowledge  of  the  diseases  of  a  country,  we  find  it  difficult 
to  understand  aright  its  history  or  its  civilization.  These 
great  diseases  have  often  destroyed  the  army  of  the  conqueror, 
or  given  the  death  blow  to  an  advancing  civilization,  and 
have  left  a  strange  and  enduring  impress  upon  the  intellectual 
life  of  great  communities.  It  is  generally  known  how,  in  the 
Fourteenth  Century,  the  most  deadly  of  all  the  pestilences  that 
are  recorded  in  past  history — the  Black  Death — changed  the 
direction  of  intellectual  and  social  activity  throughout  the 
chief  part  of  the  civilized  world,  and  showed  its  impress  on 
the  developments  of  succeeding  centuries.  We  can  gain  but 
a  faint  idea  to-day,  through  what  we  have  seen  around  us, 
of  the  devastation  that  may  be  caused  by  epidemic  diseases 
running  without  check ;  or  of  the  significance  they  have  had 
in  the  progress  of  civilization. 

The  terrible  results  of  epidemic  and  contagious  diseases 
have  furnished  the  strongest  possible  incentives  to  the  study 
of  the  underlying  causes.  In  all  ages  of  the  world  the  effort 
to  understand  them  has  been  unceasing. 


14  THE   GERM   THEORY   OF   DISEASE. 

FIRST  DEFINITE  ANNOUNCEMENT. 

The  first  definite  announcement  of  a  belief  that  disease  is 
caused  by  organic  germs,  that  I  have  found,  was  in  the  time 
of  the  Roman  Empire. 

De-re-Rustica,  Varro  and  Columella,  refer  the  origin  of 
malarious  fevers  to  the  entrance  of  low  organisms  into  the 
body.  But  they  seem  not  to  have  given  the  special  observa- 
tions upon  which  their  conclusions  were  founded.  All  along 
down  the  centuries,  the  idea  was  frequently  expressed  that  the 
plague  of  the  day  was  caused  by  minute  organisms. 

This  doctrine,  however,  obtained  wide  recognition  when 
some  sort  of  basis  for  such  theories  was  furnished  by  the 
microscopic  demonstration  of  very  minute  living  organisms, 
invisible  to  the  naked  eye.  Especially  after  the  discovery  of 
the  spermatozoa  by  Leuwenhoeck  in  1677.  These  were  then, 
and  for  years  afterwards,  supposed  to  be  real  animals.  It 
having  now  been  demonstrated,  apparently,  that  real  animals 
were  living  in  the  bodies  of  men,  the  doctrine  that  diseases 
were  caused  by  minute  organisms  spread  far  and  wide.  Among 
the  best  known  advocates  of  this  theory  were  Kirchen,  Lancici, 
Valisneri,  Raumum,  and  Linne.  But  even  those  who  best 
understood  the  theory  never  reached  anything  more  than 
rough  conceptions ;  while  many  lost  themselves  in  wild  ex- 
aggerations. The  animals  causing  disease  were  described  as 
flying  about  in  the  air,  something  like  swarms  of  insects,  with 
crooked  bills  and  sharp  claws ;  and  one  writer  proposed  to 
destroy  them  during  epidemics  by  the  blowing  of  horns  and 
the  firing  of  cannon.  We  can  readily  conceive  that  such 
fantasies  would  bring  down  ridicule  upon  the  whole  theory ; 
and  in  time  these  wild  notions  were  dissipated  and  the  germ 
theory  slept. 


ZYMOSIS.  15 

PHLOGISTON. 

But  amid  these  fantasies  there  was  a  deep  vein  of  earnest 
observation  and  thought.  Physicians  saw  a  pestilence  strike 
a  community  as  a  spark  strikes  among  shavings,  and  kindling, 
attack  person  after  person  in  society,  as  fire  would  leap  from 
house  to  house  in  a  city.  Sydenham  says  :  "  Ita  ignis  ignein 
generat  et  maligno  infectus  morbo  socium  inficit." 

Stahl  supposes  a  principle  of  inflammability  or  the  matter 
of  -fire  in  composition  with  other  bodies,  an  hypothetical 
element  supposed  to  be  pure  fire,  fixed  in  combustible  bodies, 
in  order  to  distinguish  it  from  fire  in  action  or  in  a  state  of 
liberty.  This  was  called  "  Phlogiston."  A  similar  supposi- 
tion obtained  in  regard  to  epidemic  and  contagious  diseases, 
viz.,  that  there  was  some  substance  or  force  in  man  himself, 
which,  when  once  put  in  motion,  acted  similarly  to  fire  and 
spread  with  deadly  effect.  To  this  day,  remedies  directed 
against  inflammation  or  inflammatory  conditions  are  called 
an tiph logistics.  This  theory  of  the  origin  and  propagation  of 
epidemic  diseases  seems  to  have  been  much  discussed. 

ZYMOSIS. 

Another  hypothesis  was  based  on  the  known  action  of  fer- 
ments, which  is  maintained  to  this  day,  the  present  germ 
theory  being  considered  within  the  limits  of  this  hypothesis. 
It  was  seen  that  yeast,  when  added  to  certain  compounds  con- 
taining sugar,  caused  certain  phenomena.  That  a  very  small 
quantity  of  the  yeast  was  necessary  for  a  beginning,  and  that 
this  would  be  reproduced  continuously.  It  could  be  carried 
from  vat  to  vat  of  grape  juice  for  any  number  of  times,  and 
the  more  fermentation  accomplished  the  more  the  ferment 
increased.  It  was  found,  also,  that  this  kind  of  fermentation 
would  begin,  but  less  promptly,  without  the  addition  of  yeast, 
and  that  in  this  case  also  the  yeast  was  formed.  Now  they 


16  THE   GERM   THEORY   OF   DISEASE. 

reasoned  that  the  action  of  epidemic  and  contagious  diseases 
was  the  same.  From  the  sick  person  it  seemed  that  a  sub- 
stance or  force  was  conveyed  to  the  well.  Thus,  one  sick 
person  may  infect  a  dozen,  and  each  of  these  a  dozen  more, 
etc.,  so  that  the  disease  is  rapidly  diffused  through  a  com- 
munity. It  will  be  seen  at  once  that  the  similarity  between  the 
phenomena  of  these  diseases  and  the  phenomena  of  fermenta- 
tion is  very  close.  These  two  hypotheses  gave  rise  to  much 
discussion.  They  seem  to  have  stood  side  by  side  until  the 
one  merged  into  the  other,  for  the  more  they  were  discussed 
the  more  similar  they  seemed  to  become.  Finally,  the  first  is 
lost  sight  of  and  the  Zymotic  theory  of  epidemics  and  con- 
tagions, as  developed  by  Willis  in  1659,  has  continued  to  be 
the  generally  accepted  theory. 

JENNER. 

When  Jenner  discovered  the  relation  of  the  vaccine  disease 
to  smallpox,  and  began  the  use  of  the  vaccine  virus  as  a  pro- 
tective against  that  malady  in  1798,  there  came  a  much 
greater  confidence  in  the  fermentation,  or  as  it  is  called,  the 
zymotic  theory  of  contagion.  Here  the  physician  had  a  body 
that  he  could  carry  about  and  use  at  will,  as  he  could  yeast. 
He  could  introduce  this  disease-producing  yeast,  or  virus,  into 
the  skin  of  a  healthy  person,  and  after  a  certain  time,  a  disease 
would  manifest  itself;  just  as  he  could  introduce  yeast  into  a 
solution  of  sugar,  and  after  a  certain  time,  find  the  phenomena 
of  fermentation.  A  small  amount  of  either  was  sufficient ;  in 
each  case  a  certain  period  of  rest  was  observed  before  the 
characteristic  manifestations  declared  themselves ;  a  stage  of 
incubation.  In  each  case  the  peculiar  product  first  used  was 
largely  increased.  In  case  of  the  vaccine,  a  dozen  could  be 
vaccinated  from  the  product  of  the  first  vaccination,  just  as 
from  the  product  of  the  fermentation  of  a  single  butt  of  must 


NINETEENTH   CENTURY.  17 

enough  yeast  could  be  produced  to  quickly  start  fermentation 
in  a  dozen  more;  and  so  on,  ad  infinitum,  in  both  cases.  The 
phenomena  of  the  one  following  precisely  the  role  of  the  phe- 
nomena of  the  otfcpw*  in  every  respect,  only  one  was  the  fer- 
mentation of  sugar,  and  the  other  was  the  production  of  the 
disease,  Vaccina. 

Neither  did  the  likeness  stop  here;  but,  as  we  shall  see,  it 
went  much  further.  It  was  then  well  known  that  a  certain 
amount  of  heat  destroyed  the  power  of  yeast  forever.  Trial 
showed  that  precisely  the  same  thing  happened  with  the 
vaccine  virus.  Furthermore,  it  was  well  known  that  when 
a  solution  of  sugar  has  been  under  the  process  of  fermentation 
until  that  process  has  spontaneously  ceased,  a  further  fermenta- 
tion could  not  be  had  by  adding  more  yeast;  although  un- 
fermented  sugar  may  remain  in  the  solution.  The  results 
when  completed  are  completed  once  for  all;  and  for  a  new 
trial  a  new  mixture  must  be  had.  Or  in  other  words,  the 
result  of  fermentation  prevents  fermentation  of  the  same 
character  again  taking  place.  These  phenomena  are  again 
repeated  by  the  vaccine  virus.  A  person  once  vaccinated  is 
rendered  insusceptible  to  further  vaccination;  at  least  for 
some  years.  All  these  facts  taken  together  furnished  the 
strongest  possible  proof  of  the  identity  of  the  two  processes, 
at  least  in  mode  of  operation;  however  wide  the  difference 
in  the  results.  And  the  well  known  fact,  that  in  the  great 
majority  of  the  then  known  contagious  diseases,  one  attack 
rendered  the  subject  of  it  incapable  of  again  taking  the  same 
malady,  served  to  extend  the  theory  to  all  diseases  of  this  class. 

NINETEENTH  CENTURY. 

This  is  the  condition  in  which  we  find  the  theory  of  zymotic 
diseases  at  the  beginning  of  the  present  century.  To  say  that 
this  theory  was  universally  accepted  and  satisfactory,  would 


18  THE   GERM   THEORY   OF   DISEASE. 

be  untrue.  Very  many  denied  the  relevance  of  the  facts 
brought  forward,  and  sought  other  explanations;  but  without 
gaining  much  favor.  Earnest  men  were  examining  the  act 
of  fermentation ;  and  especially  seeking  the  causes  of  putrefac- 
tion. Why  should  a  dead  body  pass  so  quickly  into  a  state 
of  putrefaction?  Enough  was  known  to  convince  many 
thoughtful  men  that  putrefaction  was  not  caused  by  anything 
inherent  in  the  flesh  itself;  for,  under  some  circumstances, 
decomposition  did  not  take  place.  They  had  learned  to  pre- 
vent it,  at  least  for  a  long  time,  in  meats  that  were  preserved 
for  food.  Many  other  circumstances  came  up  which  furnished 
food  for  thought,  and  which  shook  the  faith  in  the  idea  that 
fermentation  of  vegetable  substances  and  putrefaction  of 
animal  tissues  were  truly  spontaneous  and  inherent  in  the 
nature  of  such  bodies. 

EARLY  DISCOVERIES. 

In  the  first  decade  of  the  sixteenth  century,  Von  Helmont 
had  shown  that  the  gas  arising  from  fermentation  was  different 
from  common  air  ;  was  carbon  dioxide.  And  the  other  pro- 
duct, alcohol,  had  been  known  from  the  earliest  historic  times, 
but  it  was  not  isolated  until  the  fifteenth  century,  though  its 
distillation  was  regularly  practiced  in  the  eighth.  It  had  been 
shown  by  Gay-Lussac,  that  grape  juice  does  not  ferment  in 
vacuo.  This  was  discovered  in  a  now  classical  series  of 
experiments,  in  which  this  experimenter  caused  clean  grapes 
to  ascend  through  the  mercury  of  a  large  barometer  into  the 
Toricellian  vacuum,  and  then  crushed  them  by  means  of  a  mer- 
curial column.  This  juice  remained  unchanged,  but  the  addi- 
tion of  small  quantities  of  air  set  up  fermentation.  Stahl,  in 
1731,  arrived  at  the  conclusion  that  fermentation  and  putre- 
faction were  similar  or  identical  processes.  This  was  also  the 
opinion  of  Justus  Liebig,  one  hundred  years  later. 


EARLY   DISCOVERIES.  19 

In  1680  the  Dutch  professor  Leuwenhoeck  began  the 
examination  of  yeast  under  the  microscope,  and  found  it  to 
consist  of  minute  ovoid  or  globular  particles.  But  the  imper- 
fection of  the  instruments  of  his  time  prevented  the  discovery, 
which  seemed  so  near,  of  the  nature  of  these  particles.  Ex- 
periments of  various  kinds  were  instituted  by  many  persons,  a 
few  of  which  may  be  mentioned  :  A  bladder  was  filled  with  a 
solution  of  sugar  and  suspended  in  another  solution  of  sugar, 
to  which  yeast  had  been  added.  While  fermentation  went 
regularly  on  in  the  fluid  in  the  containing  vessel,  the  fluid  in 
the  bladder  did  not  partake  in  the  fermentation.  A  vessel  was 
divided  into  two  compartments  by  a  partition  of  filtering 
paper,  a  solution  of  sugar  placed  in  each  and  yeast  added  to 
one.  Fermentation  went  on  promptly  in  the  compartment  to 
which  the  yeast  was  added,  but  the  other  remained  free  from 
fermentation.  Many  other  experiments  are  also  recorded,  all 
tending  to  show  that  fermentation  is  something  different  from 
ordinary  chemical  action.  But  the  men  of  the  time  seemed 
unable  to  understand  the  significance  of  their  experiments, 
which,  to  us,  prove  conclusively  that  the  substance  causing 
fermentation  is  participate  and  not  soluble,  otherwise  it  would 
pass  through  the  filters  and  produce  its  results. 

In  1787  Fabroni  affirmed  that  "  the  matter  which  decom- 
poses sugar  is  a  vegeto-animal  substance;  it  resides  in  par- 
ticular utricles  in  grapes,  as  well  as  in  corn.  When  grapes 
are  crushed  this  glutinous  matter  is  mixed  with  the  sugar. 
Directly  the  two  substances  come  in  contact,  effervescence  and 
fermentation  commence." 

Astier,  in  1813,  asserted  that  "the  matter  of  ferment, 
recognized  by  Fabroni  as  an  animal  substance,  was  alive  and 
derived  its  nourishment  from  the  sugar,  whence  resulted  the 
rupture  of  the  equilibrium  between  the  elements  of  this  body. 
By  this  theory,"  said  he,  "it  is  easily  explained  that  all  the 


20  THE   GERM   THEORY   OF   DISEASE. 

causes  which  kill  animals  or  hinder  their  development  must 
be  opposed  to  fermentation "  (Schutzenberger,  page  38). 
This  seems  to  be  the  first  appearance  of  the  modern  germ 
theory  in  a  definite  form,  and  the  first  announcement  of  the 
true  theory  of  the  antiseptics.  Astier,  however,  regarded  the 
living  substance  as  composed  of  animalcules.  A  number  of 
observers  within  the  next  few  years  seem  to  have  arrived  at 
the  same  conclusion. 

SCHWAK 

The  next  real  advance  was  made  about  the  year  1838, 
when  Schwan  and  La  tour,  each  independently,  took  up  the 
microscopic  inquiry,  with  improved  instruments,  and  dis- 
covered that  the  granules  of  yeast  were  membranous  bags, 
which  exhibited  all  the  morphological  characters  of  vegetable 
cells,  and  under  proper  conditions  increased  and  multiplied,  in 
the  biological  sense.  The  conclusion  was  quickly  reached  by 
them,  that  it  was  the  life  and  growth  of  the  plant  which 
caused  the  chemical  changes  of  fermentation ;  and  that  the 
products,  carbon  dioxide  and  alcohol,  were  excrementitious 
products  of  the  plants. 

At  this  time  Schwan  was  working  on  spontaneous  genera- 
tion, which  he  very  distinctly  negatived.  He  also,  together 
with  Schultz  and  Helmholtz,  was  the  first  to  establish  the  fact 
that  putrefaction  would  not  occur  without  the  presence  of  cer- 
tain minute  organisms,  which  might  be  destroyed  by  boiling; 
and  then,  that  air  deprived  of  these  organisms  by  being  heated, 
or  by  filtering  through  sulphuric  acid,  might  be  admitted 
and  yet  no  decomposition  would  occur.  This  destroyed  the 
hypothesis  previously  held,  that  oxygen  was  the  active  agent 
in  decomposition  ;  yet  it  was  not  generally  accepted.  It  is  to 
this  discovery  that  we  owe  our  ability  to  preserve  fruits, 
meats,  etc.,  in  cans  hermetically  sealed,  which  has  conferred 
such  blessings  upon  mankind. 


LIEBIG'S  OPPOSITION.  21 

EFFECTS  OF  SCHWABS  DISCOVERIES. 
These  brilliant  discoveries  very  soon  attracted  general  at- 
tention to  the  subject  from  the  scientific  world,  and  as  iden- 
tical theories,  as  we  have  shown,  had  long  been  held  as  to  the 
modes  of  propagation  and  action  of  contagious  diseases,  and 
of  fermentation  and  putrefaction,  the  theory  of  a  contagiurn 
vivum  again  came  to -the  front,  and  was  urged  by  some  of  the 
strongest  minds  of  the  time.  The  new  theory,  however,  was 
destined  to  fight  its  way  inch  by  inch.  Every  new  fact  that 
was  put  forth  had  to  pass  the  most  rigid  criticism  that  the 
opponents  of  the  theory  could  bring  to  bear  upon  it ;  and  for 
a  time  it  seemed  as  if  it  would  be  crushed  out  of  existence 
notwithstanding  its  apparent  demonstration. 

LIEBIG'S  OPPOSITION. 

The  strongest  opponent  of  the  vital  theory,  as  it  seems  to 
me,  was  the  then  comparatively  young  Professor  of  Chemistry 
at  Giessen,  Germany,  Justus  Liebig.  Liebig' s  view  of  fer- 
mentation is  practically  the  same  as  that  enunciated  by  Willis 
in  1659,  and  maintained  by  others  in  the  succeeding  years ; 
but  it  is  in  Professor  Liebig's  writings  that  the  view  reached 
its  highest  stage  of  development  and  can  be  best  studied.  It 
merits  the  closest  scrutiny,  for  it  has  been  the  principal  oppo- 
nent with  which  the  germ  theory  has  had  to  contend.  If  we 
follow  the  contests  between  the  chemists  on  the  one  side  and 
the  vitalists  on  the  other,  up  to  the  present  time,  and  analyze 
the  arguments  adduced  by  the  chemists,  we  will  find  that  the 
very  few  new  facts  which  they  have  brought  forward  have  all 
been  based  on  the  plan  of  Liebig's  arguments.  There  has 
been  nothing  essentially  new,  nor  has  his  argument  been 
strengthened.  In  the  years  1840-42,  in  response  Jx)  an  invi- 
tation of  the  British  Association  for  the  Advancement  of  Sci- 
ence, Professor  Liebig  wrote  a  series  of  papers  upon  animal, 


22  THE   GERM   THEORY   OF   DISEASE. 

vegetable  and  agricultural  chemistry  and  the  chemical  trans- 
formations, including  the  action  of  the  different  ferments, 
yeast,  putrefaction,  contagion,  miasrn,  etc.,  in  which  he  antago- 
nized the  vital  theory  of  each  of  these  with  all  the  vigor  of  his 
wonderful  intellect,  and  for  the  time  crushed  the  rising  confi- 
dence in  the  new  theory. 

The  arguments  brought  forward  by  Liebig  may  be  summed 
up  as  follows  :  u  Fermentation  is  a  result  of  the  catalytic  action 
of  a  decomposing  body  in  contact  with  compounds  of  feeble 
molecular  affinity,  which  is  brought  about  in  accordance  with 
the  following  law  of  dynamics:  A  molecule  set  in  motion  by 
any  power  can  impart  its  own  motion  to  another  molecule 
with  which  it  may  be  in  contact."  Yeast,  he  argued,  is  a  pro- 
duct of  the  decomposition  of  gluten,  and  is  necessarily  a  de- 
composing body,  and  when  added  to  must  or  wort,  sets  up  in 
these  bodies  a  motion  of  their  molecules  similar  to  its  own,  by 
which  their  saccharine  elements  are  converted  into  the  simpler 
and  more  stable  compounds,  carbonic  acid  and  alcohol. 

But  the  action  upon  the  gluten  is  to  convert  it  into  a  body 
identical  with  the  original  yeast.  And  thus  the  yeast  seemed 
to  grow  ;  but  it  is  not  a  growth  in  the  biological  sense.  This, 
he  contended,  is  demonstrated  by  adding  yeast  to  a  pure  solu- 
tion of  sugar,  in  which  case,  although  the  fermentation  pro- 
ceeds promptly,  the  quantity  of  the  yeast  not  only  did  not 
increase,  but  actually  diminished,  being  expended  in  the  act 
of  decomposition. 

Putrefaction,  he  says,  is  just  the  same  process,  but  with  a 
different  molecular  motion.  These  molecular  motions  might 
reproduce  themselves  or  not,  as  the  substance  on  which  they 
acted  contained  the  substance  from  which  they  were  pro- 
duced or  not.  Miasms  and  contagions  were  considered  as 
being  of  the  same  character. 

His  idea  of  a  chemical  force  more  powerful  than  the  vital 


23 

force  appears,  also,  in  his  explanation  of  the  manner  in  which 
poisons  and  medicines  act.  The  manner  in  which  inorganic 
poisons  (medicines)  gain  admission  to  the  tissues  is -owing,  in 
most  cases,  to  the  formation  of  a  chemical  compound  by  the 
union  of  the  poison  with  the  constituents  of  the  organ  upon 
which  it  acts ;  it  is  owing  to  a  chemical  affinity  more  powerful 
than  the  vitality  of  the  organ.  Each  of  these  substances,  in 
its  transit,  produces  a  peculiar  disturbance  in  the  organism  ;  in 
other  words,  they  exercise  a  medicinal  action  upon  it,  but 
they,  themselves,  suffer  no  decomposition.  It  is  only  when 
the  solutions  are  diluted  to  a  certain  degree  with  water  that 
they  are  absorbed  by  auimal  tissues.  In  respect  to  this 
physical  property  of  the  animal  tissues,  alcohol  resembles  the 
inorganic  salts. 

Miasms  and  contagions  were  thus  explained:  "A  miasm  is 
a  form  of  molecular  force  developed  during  the  decomposition 
of  vegetable  bodies  under  certain  peculiar  circumstances, 
which  has  the  power  of  setting  up  similar  decompositions  in 
the  human  blood ;  but  not  finding  in  the  blood  or  tissues  the 
proper  substance  for  its  own  reproduction,  like  yeast  in  sugar, 
it  is  not  reproduced.  Therefore,  such  diseases  are  not  con- 
tagious." 

"  Contagious  poisons  find  in  the  human  blood  and  tissues 
substances  from  which  they  reproduce  themselves,  as  yeast  in 
must  or  wort  is  reproduced  from  the  gluten ;  consequently, 
these  diseases  are  conveyable  from  the  sick  to  the  well ;  in 
some  instances  by  contact  only,  as  in  syphilis,  in  which  case 
the  physical  form  of  the  substance  is  that  of  a  solid.  In 
other  instances  through  the  air,  in  which  case  the  physical 
form  is  that  of  a  gas."  He  says,  "several  kinds  of  contagions 
are  propagated  through  the  air ;  so  that,  according  to  the  view 
already  mentioned  (of  a  contagium  vivum),  we  must  ascribe 
life  to  a  gas,  that  is,  to  an  aeriform  body." 


24  THE   GERM   THEORY   OF   DISEASE. 

He  thus  recognized  a  gaseous  form  of  ferments. 

We  have  already  spoken  of  the  fact  that  when  fermentation 
spontaneously  ceased,  it  could  not  again  be  set  up ;  and  its 
application  to  those  contagious  diseases  which  can,  ordinarily, 
be  had  but  once  by  the  same  individual.  This  theory  was 
elaborated  anew  by  Liebig,  with  telling  effect  against  the  vital 
theory.  It  was  considered  that  in  must  or  wort  there  is  a 
certain  substance  that  is  decomposed  by  the  peculiar  molecular 
motion  of  vinous  fermentation,  namely,  sugar;  while  the  other 
portions  of  the  compound  are  not  necessarily  affected.  The 
blood  is  a  very  complex  substance,  containing  many  compounds 
held  together  by  feeble  molecular  affinities,  any  one  of  which 
may  be  decomposed.  In  case  of  the  contagious  diseases,  the 
decomposing  body  which  causes  the  particular  disease  acts 
upon  some  single  compound  of  the  blood,  decomposing  it. 
If  this  particular  component  of  the  blood  be  very  important 
to  the  vital  processes,  the  disease  will  be  very  grave.  If,  on 
the  other  hand,  this  particular  compound  be  not  very  im- 
portant, the  disease  will  be  correspondingly  light.  Now  in 
the  progress  of  the  disease  this  particular  compound  is  all 
decomposed,  as  the  sugar  in  grape  juice,  and  if  the  patient 
has  been  able  to  withstand  the  shock,  he  returns  to  health 
with  this  one  compound  of  the  blood  lacking,  and  it  often 
happens  that  it  is  replaced  very  slowly,  if  at  all ;  therefore, 
the  patient  is  protected  for  a  time  or  permanently. 

•Liebig  explained  the  susceptibility  of  children  to  certain 
diseases  while  adults  were  insusceptible,  by  assuming  that  the 
constituent  of  the  blood  upon  which  the  molecular  motion 
poison  acted  in  the  child  was  absent  in  the  adult.  He  also 
explained  the  differences  in  susceptibility  of  different  indi- 
viduals in  the  same  way. 

Finally,  Liebig  says,  "all  the  supposed  proofs  of  the  vitality 
of  contagions  are  merely  ideas  and  figurative  representations, 


25 

fitted  to  render  the  phenomena  more  easy  of  apprehension  by 
our  senses,  without  explaining  them.  These  figurative  ex- 
pressions, with  which  we  are  so  willingly  and  easily  satisfied 
in  all  sciences,  are  the  foes  of  all  inquiries  into  the  mysteries 
of  nature;  they  are  like  the  Fata  Morgana,  which  show  us 
deceitful  views  of  seas,  fertile  fields  and  luscious  fruits,  but 
leave  us  languishing  when  we  have  most  need  of  what  they 
promise.  It  is  certain  that  the  action  of  contagions  is  the 
result  of  a  peculiar  influence  dependent  upon  chemical  forces, 
and  in  no  way  connected  with  the  vital  principle.77 

Liebig  claimed  that  this  poisonous  substance  could  not  be 
isolated,  because  it  consisted  of  a  peculiar  form  of  molecular 
motion.  But  in  many  cases  the  substances  containing  this 
molecular  motion  poison  could  be  had,  which  substance  in 
itself  was  not  poisonous,  as  was  shown  by  exposing  it  to  heat, 
thus  rendering  it  innocuous  by  destroying  this  peculiar  mo- 
lecular power. 

He  also  points  out  the  fact  that  very  many  of  these  poisons 
are  destroyed  in  the  human  stomach  in  the  act  of  digestion, 
and  that  others  are  not.  He  explains  these  phenomena  in 
this  way.  All  of  these  ferment  poisons  owe  their  power  to 
the  peculiar  molecular  movement  started  and  maintained  by 
the  act  of  decomposition.  Now,  when  they  come  in  contact 
with  stable  compounds  they  are  unable  to  communicate  their 
own  movements  to  these  associated  molecules,  and  are  con- 
sequently inert,  or  unable  to  propagate  decomposition.  But, 
if  the  intermixed  substance  is  composed  of  molecules  held 
together  feebly,  the  molecular  movement  is  communicated  to 
them,  and  they  pass  into  a  state  of  decomposition. 

Now  the  juices  of  the  stomach  are  acid,  and  among  the 
noxious  substances  many  are  alkaline,  but  some  are  acid. 
It  therefore  happens  that  when  an  alkaline  organic  poison  or 
ferment  is  introduced  into  the  stomach,  its  molecular  force  is 


26  THE   GERM   THEORY   OF   DISEASE. 

antagonized  by  the  acid  juices  it  meets  there  and  its  molecular 
movement  destroyed. 

If,  however,  the  noxious  element  be  acid  in  its  reaction, 
the  juices  of  the  stomach  do  not  interfere  with  its  molecular 
movement,  but  rather  favor  it.  And  instead  of  being  de- 
stroyed, it  is  rendered  even  more  virulent.  This  action  of 
the  stomach,  he  argues,  is  a  very  positive  proof  of  the  chemical 
nature  of  these  poisons. 

It  is  a  noteworthy  fact  that  in  this  essay  Prof.  Liebig 
practically  ignores  the  microscopic  demonstrations  of  the  yeast 
plant.  He  evidently  regarded  it  as,  to  a  large  extent,  a  fiction 
of  the  brain  of  over-zealous  investigators,  using  what  was 
in  that  day  considered  very  high  powers  of  the  microscope. 
Not  believing  in  the  existence  of  the  yeast  plant,  or  the 
organisms  of  disease,  he  says,  "The  vital  principle  is  only 
known  to  us  through  the  peculiar  forms  of  its  instruments; 
that  is,  through  the  organs  in  which  it  resides.  Hence,  what- 
ever kind  of  energy  a  substance  may  possess,  it  is  amorphous 
and  destitute  of  organs  from  which  the  impulse,  motion  or 
change  proceeds ;  it  does  not  live." 

The  basis  which  he  gives  for  the  proof  of  the  existence  of 
life  stands  to-day  in  its  full  power.  And  if  he  is  at  last 
beaten  in  the  argument,  it  is  because  facts  have  been  brought 
forward  and  proven  by  incontrovertible  observation  that  will 
satisfy  this  basis.  This  basis  is  contained,  practically,  in  one 
sentence,  which  I  quote:  "Our  notion  of  life  involves  some- 
thing more  than  mere  reproduction,  namely,  the  idea  of  an 
active  power  exercised  by  virtue  of  a  definite  form,  and  pro- 
duction and  generation  in  a  definite  form." 


DIFFICULTIES.  27 

DIFFICULTIES. 

From  that  time  to  the  present  the  controversy  has  been 
unceasing.  Those  who  believed  that  the  vital  theory  was 
true  still  maintained  it,  for  they  had  seen  definite  forms  re- 
produced in  definite  forms,  by  virtue  of  definite  forms.  They 
returned  to  their  microscopes  and  followed  again  the  growth 
of  the  yeast  plant.  They  saw  again  the  buds  given  off  from 
the  cells,  and  reproduce  other  cells,  like  in  every  respect  to 
the  mother  cell;  and  these  in  turn  reproduce  other  cells  of 
the  same  likeness;  satisfying  the  basis  as  given  by  Prof. 
Liebig. 

But  the  microscopes  of  that  day  were  poor,  trained  ob- 
servers were  scarce,  the  subject  was  new,  the  modes  of  de- 
monstration were  comparatively  clumsy,  and  in  many  respects 
faulty.  Under  these  difficulties  progress  was  exceedingly 
slow,  at  best;  and  for  a  time  no  substantial  advance  was 
made.  But  gradually,  as  the  number  of  the  observers  of  it 
increased,  the  yeast  plant,  as  the  active  principle  of  yeast,  and 
upon  which  its  action  was  dependent,  was  accepted  by  a  large 
proportion  of  the  learned  men  of  the  world.  It  is,  however, 
a  noteworthy  fact  that  many  of  those  who  accepted  this  re- 
fused to  accept  the  vital  principle  for  the  other  fermentations; 
which  would  seem  naturally  to  follow.  This  refusal  seems  to 
have  found  a  basis  in  certain  arguments  brought  forward  by 
Prof.  Liebig,  especially  such  as  the  following :  If  oxamide  be 
brought  in  contact  with  oxalic  acid  dissolved  in  water,  the 
following  changes  take  place :  the  oxamide  is  decomposed  by 
the  oxalic  acid,  provided  the  necessary  conditions  for  their 
exercising  an  action  on  each  other  be  present.  Although  the 
oxamide  is  not  at  all  soluble,  the  elements  of  water  unite 
with  it,  and  ammonia- is  one  product  formed  and  oxalic  acid 
the  other,  both  in  the  proportions  to  form  a  neutral  salt. 
Here  the  contact  of  the  oxamide  and  the  oxalic  acid  induces 


28  THE   GERM   THEORY   OF   DISEASE. 

a  transformation  of  the  oxamide,  which  is  decomposed  into 
oxalic  acid  and  ammonia.  As  much  oxalic  acid  exists  after 
the  decomposition  as  was  added,  and  still  possesses  its  original 
power;  and  more  oxamide  will  be  decomposed  in  the  same 
way,  if  added.  This  may  be  kept  up  continuously,  and  any 
amount  of  the  oxamide  decomposed,  by  a  very  minute  por- 
tion of  the  oxalic  acid. 

Quite  a  number  of  similar  chemical  decompositions  are 
known,  and  while  they  cannot  be  considered  as  bodies  in  a 
state  of  decomposition,  as  Liebig  claimed  the  excitors  of 
fermentation  were,  the  processes  had  long  been  considered  as 
very  closely  related.  Now  as  these  processes  were  admitted 
by  all  to  be  purely  chemical,  no  process  should  be  considered 
vital  until  it  was  definitely  proven. 

This  required  that  each  one  of  these  be  investigated  on  its 
own  merits  and  proven  independent  of  all  others. 

In  this  work  the  theory  has,  perhaps,  suffered  as  much  from 
its  over-zealous  followers,  who  hastily  published  untenable 
views,  arrived  at  by  hasty  and  ill-digested  experiments,  as 
from  its  opponents. 

SCHROEDER. 

Schroeder  was,  perhaps,  the  first  to  make  a  new  and  sub- 
stantial point  that  has  stood  the  test  of  adverse  criticism.  As 
we  have  stated,  Schwan  had  demonstrated  that  decomposition 
would  not  occur  in  sterilized  fluids  upon  the  introduction  of 
air  that  had  been  heated  or  passed  through  sulphuric  acid. 
This,  as  a  demonstration  of  the  existence  of  life,  was  appa- 
rently demolished  by  Liebig,  who  claimed  that  the  heat,  or  the 
acid  either,  was  sufficient  to  destroy  the  molecular  motion  upon 
which,  as  he  claimed,  the  power  of  ferments  depended.  Now 
Schroeder,  in  1854,  admitted  air  filtered  through  cotton 
batting,  with  the  idea  that  this  would  catch  any  solid  par- 
ticles in  the  shape  of  spores  or  germs.  His  experiment  was  a 


SCHROEDER.  29 

perfect  success.  Sterilized  fluids  kept  just  as  perfectly  when 
sealed  with  a  wad  of  cotton,  as  when  sealed  hermetically. 
This,  as  it  became  established,  effectually  disposed  of  the 
theory  of  gaseous  ferments.  But  the  claim  was  now  made 
that  the  dried  remains  of  decomposing  bodies  might  fly  about 
in  the  air  and  renew  their  molecular  motions  on  being  again 
moistened,  and  that  these  would  be  kept  out  of  sterilized 
fluids  by  the  cotton  batting,  the  same  as  was  claimed  for 
living  germs. 

The  following  are  the  conclusions  of  Schroeder : — 

1st.  "  All  vegetable  or  animal  forms  derive  their  origin 
from  other  living  vegetable  or  animal  beings.  Omne  vivum 
ex  vivo. 

2d.  "  When  a  series  of  specific  products  of  fermentation 
and  putrefaction  are  developed  at  a  certain  spot,  germs  which 
originate  the  process  have  been  conveyed  to  that  spot  through 
the  medium  of  the  air.  Such  is  certainly  always  the  case  with 
regard  to  germs  of  mould,  and  to  the  ferments  of  wine,  milk 
and  urine. 

3d.  "  Vegetable  and  animal  matter  in  which  all  germs 
have  been  destroyed  by  boiling,  and  which,  while  yet  in  a 
hot  state,  has  been  shut  off  from  the  direct  influence  of  the 
external  air  by  means  of  cotton- wool,  remains  perfectly  free 
from  mould,  fermentation  or  putrefaction.  The  germs,  which 
otherwise  would  be  supplied  by  the  air,  are  arrested  in  the 
passage  of  the  latter  through  the  cotton-wool. 

4th.  "  The  germs  of  most  vegetable  and  animal  substances 
are  destroyed  by  exposure  for  a  short  time  to  a  temperature  of 
100°  C.  (212°  F.) 

5th.  "  But  milk,  yelk  and  meat  contain  germs  which  are 
not  thus  killed.  Boiling  at  a  high  temperature,  under  higher 
pressure,  or  long-continued  boiling  at  100°  C.,  will,  however, 
always  suffice  to  destroy  these  germs. 


30  THE   GERM   THEORY   OF    DISEASE. 

6th.  "  The  germs  in  milk,  yelk  of  eggs  and  meat,  after 
having  been  boiled  a  short  time,  are  still  capable  of  being  de- 
veloped into  the  specific  ferment  of  putrefaction,  and  some- 
times, also,  those  of  yelk ;  at  least,  into  long  and  indolent 
vibriones. 

7th.  "  The  specific  ferment  of  putrefaction  is  of  an  animal 
nature.  It  develops  itself  and  multiplies  at  the  expense  of 
albuminous  compounds,  but  does  not  multiply  under  those 
conditions  alone  which  supply  all  the  requisites  for  vegetable 
growth."  (Sydenham  Society's  Year  Book  for  1862.  An- 
nalen  der  chemie  u  pharmacie,  vol.  117.) 

PASTEUR. 

The  next  important  advance  may  be  best  illustrated  by  the 
labors  of  M.  Pasteur,  in  his  sealed-flask  cultivations,  although 
he  was  not  the  first  to  employ  this  particular  mode  of  study. 
Shutzenberger  mentions  that  this  kind  of  cultivation  was  first 
performed  by  Needham,  in  London,  who  published  a  work  on 
this  subject  in  1745,  in  which  it  seems  that  he  maintained  the 
hypothesis  of  the  de  novo  origin  of  infusoria.  Spallanzani,  a 
celebrated  Italian  physiologist,  took  the  matter  up,  which  re- 
sulted in  a  lengthy  controversy,  in  which  Spallanzani  refuted, 
by  experiment,  the  conclusions  of  Needham.  The  contro- 
versy turned  on  this  point.  Spallanzani  was  not  satisfied  with 
heating  the  hermetically  sealed  flasks  containing  the  infusion 
for  several  minutes,  merely  the  time  required  to  cook  a  hen's 
egg  and  destroy  the  germ,  as  Needham  expressed  it,  but  he 
kept  them  boiling  for  an  hour ;  after  which  no  infusoria  were 
found.  (Shutzenberger  on  Fermentation,  page  311.) 

The  plan  of  Pasteur  was  practically  this :  He  reasoned 
that  if  he  could  grow  the  yeast  plant  in  sealed  flasks  until  all 
gluten  with  which  it  was  first  connected  could  be  certainly  got 
rid  of,  he  could  then  study  the  plant  in  all  its  purity,  and 


PASTEUE.  31 

effectually  disprove  the  molecular  motion  theory.  He,  there- 
fore added  a  small  quantity  of  yeast;  as  pure  as  possible,  to 
some  cultivation  fluid  which  had  been  effectually  sterilized  by 
heat  and  contained  no  gluten,  and  carefully  sealed  it.  After 
this  had  passed  through  the  stage  of  fermentation,  another 
flask  was  prepared  in  the  same  way;  and  under  the  utmost 
precautions  that  nothing  else  should  be  introduced  from  with- 
out, a  drop  was  taken  from  the  first  with  a  pipette,  and  added 
to  the  second,  and  so  on,  to  the  fiftieth  generation,  and  in  many 
of  his  experiments  more  than  this  number.  These  flasks 
were,  of  course,  kept  at  the  proper  temperature  for  the  develop- 
ment of  fermentation.  The  result  of  this  series  of  experiments 
seemed  to  satisfy  Liebig's  basis  for  the  recognition  of  living 
beings;  the  yeast  plant  reproducing  itself  after  its  own  form, 
for  generation  after  generation,  continually,  and  after  the 
fiftieth  or  the  one  hundredth  generation,  again  producing  its 
characteristic  effects  upon  must  or  wort,  namely,  vinous  fer- 
mentation. They  did  more  than  this.  It  is  well  known  that, 
under  certain  conditions  of  temperature,  vinous  fermentation 
passes  into  acetic  fermentation,  with  the  production  of  vinegar. 
Now,  in  his  investigations,  Pasteur  found  that  he  was  able  to 
separate  these  forms  of  fermentation  by  special  management 
of  the  cultures.  By  taking  at  the  beginning  a  fermentation 
contaminated  by  the  acetic  process  and  keeping  the  temperature 
high,  the  acetic  acid  plant,  the  microderma,  flourished,  while 
the  vinous  plant,  the  torula,  gradually  died  out.  He  thus 
rendered  the  conditions  unfavorable  to  the  one  and  favorable 
to  the  other ;  and  by  this  operation  and  the  reverse  one  he 
succeeded,  after  passing  the  culture  through  many  generations, 
in  obtaining  the  vinous  yeast  plant  entirely  pure,  and  the 
acetic  yeast  plant  entirely  pure,  each  of  which  would  al- 
ways produce  its  characteristic  fermentation  and  nothing  else. 
And  what  is  more,  he  found  the  plants  to  be  characterized  by 


32  "  THE   GERM   THEORY   OF   DISEASE. 

different  forms,  which  remained  constant.  I  use  this  simply 
as  an  illustration  of  the  plan  of  what  was  known  as  fractional 
cultivations.  The  same  was  done  with  the  lactic  acid  fer- 
mentation, and  its  characteristic  plant  isolated  and  established. 
In  time  and  by  this  process  several  others  have  been  success- 
fully isolated  and  established,  until  all  of  the  processes  here- 
tofore known  as  fermentations  have  been  certainly  connected 
with  living  organisms,  without  which  none  of  them  can  succeed. 

Pasteur,  after  working  out  vinous  and  acetic  fermentations, 
and  that  peculiar  fermentation  which  destroys,  in  its  turn, 
the  vinegar,  has  followed  up  the  process  of  the  complete 
return  of  the  fruit  \o  the  primitive  inorganic  state. 

After  the  fermentation  of  the  vinegar,  Pasteur  next  ex- 
amined the  putrid  fermentations,  or  decompositions,  as  they 
are  usually  called.  The  principal  agents  in  these  he  found 
to  be  certain  very  active  bodies  which  he  called  vibrios,  and 
which  multiply  with  remarkable  rapidity  in  the  depths  of  the 
mass,  as  much  as  possible  apart  from  oxygen.  This  charac- 
teristic position  serves  to  distinguish  them  from  the  ordinary 
bacteria,  which  require  oxygen  for  their  growth  and  are  found 
near  the  surface.  9 

These  vibrios  of  Pasteur  are  the  proper  authorities  which 
administer  upon  the  ruined  estates  of  dead  bodies,  animal  and 
vegetable. 

Countless  swarms  of  bacteria  may  assist  them,  by  their 
presence  near  the  surface,  by  fixing  any  oxygen  which  would 
otherwise  be  absorbed  by  the  fluid  and  hinder  the  work  of 
the  vibrios,  which  work  without  free  oxygen.  Pasteur  has 
grown  these  vibrios  in  flasks,  from  which  every  particle  of 
free  oxygen  has  been  removed,  and  found  them  to  be  the 
true  agents  of  decomposition. 

His  fluid  for  this  purpose  was  prepared  by  placing  in  a 
three-liter  flask  of  water  the  following  salts  : — 


PASTEUR.  33 

Pure  lactate  of  lime Grams     75.0 

Phosphate  of  ammonia u  0.5 

Phosphate  of  potash "          0.4 

Chloride  of  magnesium a          0.3 

Sulphate  of  ammonia "          0.2 

Sulphate  of  soda a  trace. 

Pasteur  has  also  cultivated,  individually,  many  other  organ- 
isms, and  noted  their  peculiarities.  The  extreme  high  tem- 
perature borne  by  the  spores  of  the  ordinary  moulds  is  very 
wonderful.  For  instance,  the  Penicilliurn  Glaucum  grew 
after  being  exposed  for  a  considerable  time  to  a  dry  heat 
of  248°  F.  and  257°  F.  It  was  the  same  with  the  spores  of 
other  mucidiues.  At  266°  F.  the  power  of  growth  was  lost 
in  them  all. 

Spores  of  the  bacterium  lactis  were  destroyed  at  250°  F. 

Pasteur  also  made  many  experiments  to  determine  the 
prevalence  of  germs  in  the  air.  He  placed  fermentable 
fluids  in  flasks,  boiled,  and  sealed  them  while  hot;  after 
they  were  cold  he  broke  the  end  of  the  tube,  letting  the  air 
enter  unmodified,  then  sealed  them  again  at  once.  It  often 
happened  that  no  organisms  developed  in  these  flasks,  but 
they  generally  did  in  Paris.  In  the  open  country  only  eight 
out  of  twenty  developed  germs.  On  the  Jura  only  five  out 
of  twenty.  On  Mountanvert,  in  a  wind  blowing  from  a 
glacier,  only  one  out  of  twenty  contained  germs. 

There  was  one  point  of  failure  in  Pasteur's  work  which  it 
seemed  impossible  to  settle  by  his  plan.  In  all  his  experi- 
ments the  organisms  are  transferred  to  his  flasks  together  with 
a  minute  portion  of  the  fermenting  fluid  containing  them. 
Now  the  claim  is  made  that  it  is  this  minute  portion  of  decom- 
posing fluid  that  sets  up  and  maintains  the  act  of  fermenta- 
tion, instead  of  the  organisms,  as  claimed  by  Pasteur.  This 
claim  has  much  influence  with  all  those  who  are  inclined  to 
the  views  of  Baron  Liebig,  and  its  force  must  be  admitted. 


31  THE   GERM   THEORY   OF   DISEASE. 

Pasteur's  work  made  a  very  marked  impression  upon  the 
opinions  held  by  the  scientific  world.  Although  the  general 
facts  as  developed  had,  in  a  measure,  been  accepted  before, 
there  had  not  been  so  clear  a  demonstration  of  them.  The 
result  was  a  vast  increase  of  confidence  in  the  germ  theory  of 
disease,  as  held  by  Schwan  and  others  nearly  a  quarter  of  a 
century  before.  And  when  Liebig  wrote  his  last  paper  on 
this  subject  in  1870,  reaffirming  his  old  doctrine,  with  some 
modifications,  it  produced  but  little  impression  upon  the  grow- 
ing faith  in  the  new  doctrine,  which  now  numbered  among  its 
adherents  a  large  number  of  the  most  thoughtful  and  best 
informed  scientists.  (See  Half-yearly  Compendium,  July, 
1870,  page  38,  for  Brief  of  Liebig's  article.) 

The  following  statement  contains  Pasteur's  conclusions : 
t(  The  chemical  act  of  fermentation  is  essentially  a  correlative 
phenomenon  of  the  vital  act,  beginning  and  ending  with  it. 
.  .  .  There  is  never  any  fermentation  without  there  being 
at  the  same  time  multiplication  of  globules,  or  the  continued 
consecutive  life  of  globules  already  formed." 


SECOND  LECTURE. 

BASTIAN. 

The  presentation  of  this  subject  would  be  incomplete  with- 
out some  reference  to  the  view  of  the  de  novo  origin  of  life, 
"  Archebiosis."  This  view  has  been  held  by  learned  men  in 
all  historical  ages  of  the  world,  though  it  has  never,  at  any 
time,  been  generally  adopted.  Such  a  view  was,  perhaps, 
more  prevalent  in  the  fourteenth  and  fifteenth  centuries  than 
at  any  other  time  in  the  world's  history.  Bastian,  the  great- 
est exponent  of  that  view,  however,  lives  in  the  present,  and 
I  have  thought  best  to  defer  mention  of  it  to  this  time, 
especially  as  it  affects  our  subject,  "  The  Germ  Theory  of 
Disease/7  only  incidentally. 

This  great  experimentalist,  in  his  theories,  does  not  depart 
markedly  from  the  theory  held  by  the  chemists  and  vitalists, 
but  in  a  large  degree  adopts  the  views  of  both  and  forms  a 
connecting  link  between  the  two.  It  is,  also,  Here  again  note- 
worthy that  the  facts  developed  by  either  and  both  these  are 
made  to  serve  Dr.  Bistian's  purpose  almost  as  well  as  those 
developed  by  himself.  Taking  the  molecular  movement 
theory,  as  developed  by  the  great  exponent  of  that  view  of 
fermentation,  Liebig,  he  claims  that  this  same  molecular 
movement,  under  certain  circumstances,  actually  passes  over 
into  vital  manifestations,  furnishing  the  living  forms  found 
in  the  culture  fluids  contained  in  the  experimental  flasks  of 
Pasteur. 

He  claims  to  have  produced  these  living  forms  experiment- 
ally, especially  from  infusions  of  hay  and  turnips,  which  he 
first  boiled  in  his  flasks,  and  while  boiling,  hermetically  sealed, 


36  THE   GERM   THEORY   OF   DISEASE. 

and  afterward  exposed  to  favoring  conditions  of  temperature 
and  light.  With  these  and  other  infusions  treated  in  this 
manner,  he  found  within  a  few  days  multitudes  of  living 
forms. 

In  order  that  these  shall  develop,  he  says  that  the  flasks 
should  not  be  more  than  half  or  one-third  full,  and  that 
above  the  fluid  there  should  be  a  partial  vacuum.  When  it 
was  urged  against  his  conclusions,  that  the  temperature  was 
not  sufficiently  high,  nor  sufficiently  prolonged,  he  increased 
both,  running  the  temperature  to  300°  F.,  but  still  obtained 
the  same  result. 

Dr.  Bastian  enters  into  a  very  exhaustive  argument,  using 
the  facts  developed  by  both  the  chemists  and  vitalists,  for 
the  maintenance  of  his  theory. 

He  claims,  stoutly,  that  the  molecular  motion  theory  of 
Liebig  is  the  true  one,  as  far  as  it  goes,  but  does  not  go  far 
enough,  and  quotes  largely  from  him,  while  he  also  claims 
that  the  fermentation  theory  of  the  vitalists  is  true,  from  the 
point  where  they  begin,  but  they  do  not  begin  early  enough, 
and  quotes  largely  from  them.  In  a  word,  Dr.  Bastian  claims 
that  these  two  theories  are  the  opposite  ends  of  a  complete 
cycle  of  manifestations,  with  the  middle  and  most  important 
manifestations  left  out  by  both  parties;  i.  e.,  that  the  one 
passes  over  into  the  other. 

He  takes  the  case  of  the  production  of  vinegar.  In  the 
ordinary  and  natural  production  of  vinegar,  the  fermentation  is 
always  accompanied  by  the  presence  of,  or  as  Dr.  Bastian  claims, 
the  production  of,  the  plant  known  as  the  Mycoderma  Aceti. 

The  chemists  claim  that  this  plant  is  an  accident  of  the 
fermentation,  and  not  necessary  to  the  operation,  and  succeed 
by  other  means  in  producing  vinegar,  without  the  presence  of 
the  plant. 

The  vitalists  admit  the  production  of  vinegar  by  purely 


BASTIAN.  37 

chemical  means,  claiming  that  this  production  is  not  properly 
by  fermentation,  and  cite  the  fact  that  the  oil  of  almonds  and 
a  host  of  other  substances  naturally  vegetable  products  may 
be  produced  by  the  chemists  through  purely  chemical  pro- 
cesses. Dr.  Bastian  now  claims  that  both  processes  of  the 
production  of  vinegar  are  fermentative,  and  that  the  second 
form  (vital)  is  a  more  fully  developed  form  of  the  first 
(chemical),  and  that  the  one,  under  favoring  conditions,  will 
pass  over  into  the  other  without  any  introduction  of  germs. 

Other  scientists  and  experimentalists  have  very  generally 
denied  the  correctness  of  Dr.  Bastian's  results,  and  set  up 
the  claim  that  he  has  not  used  sufficient  care  in  the  exclusion 
of  germs,  or  that  the  heat  to  which  his  infusions  were  ex- 
posed was  not  sufficiently  high,  or  not  repeated  sufficiently 
often,  to  destroy  germs  or  spores  not  yet  hatched.  Moreover, 
other  experimenters  have  failed  to  confirm  his  results.  What- 
ever be  the  final  judgment  as  to  the  correctness  of  Dr.  Bastian's 
views,  it  is  certain  that  this  course  of  experiments  and  the 
discussion  which  they  invoked  greatly  extended  our  know- 
ledge of  the  preserving  of  fruit  in  cans,  so  that  we  are  now 
able  to  preserve  articles  which  previously  had  resisted  our 
efforts.  One  of  these  is  green  corn,  which  seems  to  require  that 
it  be  sealed  up  at  the  boiling  temperature,  and  then  boiled  for 
a  number  of  hours  each  day  or  two,  until  five  or  six  boilings 
have  been  had. 

This  is  accounted  for  in  this  way.  The  spores  of  certain 
organisms  find  green  corn  a  very  suitable  soil  for  their  de- 
velopment, and  while  the  boiling  temperature  will  destroy 
the  developed  organisms  it  will  not  aifect  the  spores.  There- 
fore these  must  be  hatched  and  then  destroyed.  Hence  the 
intervals  of  boiling  must  be  continued  from  time  to  time, 
until  all  spores  are  hatched  and  destroyed.  After  which  the 
corn  will  keep  for  any  length  of  time. 


38  THE   GERM   THEORY   OF   DISEASE. 

LOGICAL  SEQUENCE. 

We  may  now  turn  our  attention  especially  to  the  germ 
theory  of  disease;  and  in  doing  so,  it  will  be  necessary  to  go 
back  to  the  discoveries  of  Schwan  and  Latour.  It  was  shown 
that  after  the  discovery  that  vinous  fermentation  was  depend- 
ent upon  the  yeast  plant,  it  was  at  once  assumed  that  all  other 
fermentations,  decompositions,  miasms  and  contagions  were 
also  dependent  upon  the  life  force. 

This  assumption  was  a  logical  sequence  to  the  then  existing 
ideas,  for  it  had  long  been  held  by  the  wisdom  of  the  world 
that  all  these  processes,  including  contagions  and  miasms,  were 
of  the  same  order,  of  the  same  genus,  and  were  brought  about 
by  forces  of  the  same  nature.  But  when  this  assumption  was 
put  forth  under  the  new  phase  of  the  matter  resulting  from 
the  discoveries  of  Schwan  and  Latour,  it  was  vehemently 
denied  by  a  host  of  scientific  men,  even  among  many  who 
accepted  the  yeast  plant  as  the  true  explanation  of  vinous  fer- 
mentation. 

DIFFICULTIES. 

This,  as  we  have  seen,  rendered  it  necessary  that  the  facts 
of  each  process  heretofore  regarded  as  fermentation  should  be 
proven  upon  its  own  merits. 

The  work  was  at  once  begun,  and  the  more  ordinary  fer- 
mentative processes  were  developed  with  considerable  rapidity, 
and  have  finally  been  completely  worked  out  and  definitely 
settled,  as  has  been  shown. 

The  proof,  however,  that  the  ordinary  decompositions,  con- 
tagious and  miasms  belonged  to  the  same  class  and  were 
brought  about  in  the  same  manner,  was  maintained  with  but 
slight  success. 

The  organisms  found  in  these  were  of  a  different  order  and 
the  most  of  them  more  minute,  and  for  a  long  time  it  was  im- 
possible to  classify  them.  Manufacturers  of  microscopes  were 


DIFFICULTIES.  39 

urged  to  make  improvements  in  object  glasses,  in  order  that 
these  minute,  ever  busy  objects  might  be-  better  seen.  And 
the  observer  was  compelled  to  await  the  tedious  operations  of 
the  maker  of  microscopes  before  he  could  proceed  satisfactorily 
with  his  work,  and  then  usually  found  that  the  gain  was  but 
slight. 

The  subject  became  more  and  more  complex  the  more  it 
was  studied.  It  was  found  that  in  each  decomposition  there 
were  varieties  of  organisms.  When  one  person  found  an 
organism  which  he  regarded  as  distinctive  of  a  certain  process 
or  disease,  and  published  his  results  to  the  world,  it  was 
usually  quickly  shown  that  this  same  organism  was  to  be 
found  in  widely  different  situations,  entirely  disconnecting  it, 
as  a  cause,  with  the  processor  disease  claimed. 

This  kind  of  disappointment  recurred  time  after  time,  until 
many  of  the  best  men  turned  away  from  the  subject  with  dis- 
gust, believing  the  theory  incapable  of  demonstration. 

It  was  proven  beyond  question  that  many,  at  least,  of  the 
bacteria  were  incapable  of  producing  disease,  and  the  view 
that  these  forms  were  the  accidents  of  the  process,  merely 
accompaniments,  were  mere  scavengers  and  had  no  causative 
relation  to  it,  gained  wide  credence. 

There  was  much  reason  for  this  view.  It  was  in  harmony 
with  what  is  seen  to  be  going  on  around  us  every  day. 
Animals  are  found  everywhere  that  do  the  work  of  the 
scavenger.  As  the  buzzards  flock  to  the  dead  carcass,  so  the 
bacteria  swarm  on  the  decompositions. 

However,  a  hawk  is  sometimes  found  among  the  buzzards, 
for  the  want  of  the  opportunity  of  attacking  living  prey,  and 
if  the  two  were  diminished  in  size  to  the  mere  specks  -which 
represent  the  bacteria,  the  work  of  distinguishing  between 
them  would  be  difficult  indeed.  In  surgery  especially,  cases 
were  continually  occurring  which  seemed  to  indicate  that  the 


40  THE   GERM   THEORY   OF   DISEASE. 

apparent  scavengers  became  the  destroyers  of  living  structures, 
and  there  was  still  a  large  number  of  workers  who  believed 
that  the  distinctive  features  of  these  organisms  could  and 
would  be  developed  in  the  course  of  time,  and  they  continued 
the  work  steadily  and  firmly. 

MODES  OF  PEOPAGATION. 

Knowledge  of  these  organisms  was  gradually  extended. 
They  were  gradually  divided  into  groups,  according  to  their 
forms  and  modes  of  propagation.  They  have  been  found  to 
multiply  in  three  different  ways. 

1st.  By  simple  budding,  as  in  the  yeast  plant. 

2d.  By  fission,  in  which  one  individual  simply  divides 
into  two. 

3d.  By  true  spores  or  eggs,  developed  in  their  interior,  as 
eggs  are  developed  in  the  interior  of  the  segments  of  the 
tapeworm. 

The  forms  are  quite  numerous.  The  round  and  oval  forms 
are  called  micrococci,  and  the  short,  stem-like  forms  bacilli ; 
the  spiral  forms  spirilli ;  while  a  large  number  remain  with 
the  common  name  bacteria  connected  with  a  descriptive 
adjective,  as  bacteria  termo. 

More  recently  the  name  of  the  disease  found  to  be,  or  sup- 
posed to  be,  produced  by  the  particular  form  has  been 
attached,  as  bacillus  anthrax,  bacillus  tuberculosis,  etc. 

Many  other  names  have  been  used,  but  those  given  seem 
now  to  be  taking  their  places.* 

*  Any  one  who  wishes  to  study  these  forms  particularly  should  have 
Cohn's  Classification,  which  is  the  most  complete  yet  made  out,  and  will 
doubtless  serve  as  the  basis  of  all  future  efforts  in  this  direction.  Magnin, 
in  his  little  book,  "  Bacteria,"  gives  this  classification  in  very  convenient 
form. 


UTILIZING   DISCOVERIES.  41 

UTILIZING  DISCOVERIES. 

Schroeder's  discovery,  in  1854,  that  the  ferments  floating  in 
the  air  could  be  filtered  out  by  cotton  batting,  together  with 
the  confirmation  of  Schwan's  conclusions  by  Pasteur,  who 
had  continued  his  fractional  cultivations,  applying  them  to 
the  decompositions,  led  to  an  effort  to  make  use  of  these  dis- 
coveries in  the  treatment  of  wounds,  although  at  that  time  no 
individual  bacterium  had  been  proven  to  be  the  cause  of 
disease. 

However,  microscopic  investigation  had  shown  that  they 
were  abundant  in  wound  secretions,  and  especially  abundant 
in  those  that  took  on  a  bad  condition. 

These  facts,  together  with  the  favorable  course  usual  with 
comminuted  fractures  in  which  the  skin  was  not  broken,  as 
compared  with  similar  fractures  with  the  skin  broken,  caused 
many  to  regard  the  difference  as  in  some  way  connected  with 
the  bacteria. 

Heretofore,  this  difference  in  the  healing  of  such  wounds 
had  been  charged  to  the  admission  of  the  oxygen  of  the  air ; 
which  had  formerly  been  supposed  to  be  the  active  agent  in 
fermentation  and  decomposition.  It  had  now  been  shown, 
experimentally,  by  Schwan  and  Latour,  and  recently  con- 
firmed in  the  most  decisive  manner  by  Pasteur,  that  the 
fermentations  and  decompositions  were  caused  by  organic 
germs. 

Schroeder  had  demonstrated  that  these  germs  could  be 
filtered  out,  and  the  air  thus  treated  would  not  cause  de- 
composition. The  old  hypothesis  was  completely  disproved  ; 
and  it  was  most  natural  to  the  thought  of  the  time  to  ascribe 
the  difference  to  the  introduction,  through  the  medium  of  the 
air,  of  the  germs  of  bacteria. 

Following  up  this  train  of  thought,  Mr.  Lister,  then  of 
Glasgow,  Scotland,  was  the  first  to  make  a  determined  effort 


42  THE   GERM   THEORY   OF   DISEASE. 

to  reduce  it  to  practice  in  surgery.  Antiseptics  had  already 
been  long  known,  and  Mr.  Lister  began  his  operations  by 
thoroughly  disinfecting  his  own  hands,  all  instruments,  sponges, 
and  everything  that  would  come  in  contact  with  the  wound, 
including  the  patient's  skin  in  the  neighborhood  of  the  part 
to  be  operated  upon.  He  then  caused  the  air  in  which  the 
operation  was  done  to  be  disinfected  by  a  continuous  spray 
of  dilute  carbolic  acid,  until  the  wound  was  closed.  Finally 
the  wound  was  so  sealed  up  as  to  prevent  the  ingress  of  germs 
from  without.  He  found  in  actual  practice  that  operation 
wounds  thus  treated  generally  healed  without  inflammation, 
and  without  one  drop  of  pus ;  simulating  in  every  respect 
the  healing  of  subcutaneous  wounds.  The  publishing  of  these 
results  by  Mr.  Lister,  in  1865,  startled  the  surgeons  of  the 
world,  and  many  grave  heads  shook  doubtingly,  as  the  words 
were  pondered. 

The  new  plan,  however,  was  tried,  far  and  wide.  It  was  a 
matter  that  every  skillful  surgeon  could  do  for  himself,  test 
for  himself,  and  judge  of  for  himself.  Although  failures 
were  made,  the  aggregate  of  results  were  so  vastly  superior 
to  anything  heretofore  attained,  that  it  completely  revolu- 
tionized hospital  practice  throughout  Europe. 

EXPLANATORY. 

This  statement  requires  a  word  of  explanation.  The  effect 
was  not  so  much  felt  in  private  practice,  or  in  small  private 
institutions.  The  reason  for  this  difference  may  be  explained 
in  this  way.  It  had  long  been  demonstrated  that  large  public 
hospitals  became  unfavorable  to  operation  or  accident  wounds. 
In  large  institutions,  all  open  wounds  were  prone  to  take  a 
bad  course  as  compared  with  similar  wounds  in  private  prac- 
tice. The  supposition  that  such  hospitals  became  infected 
with  this  class  of  disease-producing  germs  had  already  been 


NATURE   OF   THE   EVIDENCE.  43 

widely  entertained ;  and  now  the  antiseptic  method  of  Lister 
was  found  to  remove  the  difficulty,  and  render  the  treatment 
of  wounds  in  such  hospitals  as  effective  and  safe  as  the  same 
class  of  wounds  in  private  practice,  and  in  most  cases  even 
more  so.  This  grand  achievement  of  the  germ  theory  lent 
an  immense  impulse  to  the  study  of  the  subject.  Every  great 
surgeon  became  a  student  of  fermentative  change,  and  of  the 
influence  of  living  organisms,  no  matter  what  his  bias  on  the 
subject.  As  might  reasonably  be  expected  a  corresponding 
advance  has  been  attained. 

Up  to  that  time  no  one  particular  organism  had  been 
singled  out  and  proven  to  stand  in  a  causative  relation  to 
any  one  disease. 

But  now  the  study  of  the  individual  character  of  the 
organisms  found  in  wound  secretions,  and  in  the  tissues 
immediately  after  death  from  particular  diseases,  sprang  to 
the  front,  and  has  been  carried  forward  by  the  most  acute 
minds  of  our  times. 

NATURE  OF  THE  EVIDENCE. 

We  may  now  turn  our  attention  to  the  examination  of  the 
evidence  upon  which  these  views  were  based.  The  theory,  so 
far  as  it  relates  to  the  production  of  disease,  has  been  founded 
on  fragmentary  evidence,  not  upon  demonstration.  And  it 
must  be  said,  also,  that  much  of  this  fragmentary  evidence 
has  been  of  the  nature  of  what  lawyers  would  call  circum- 
stantial evidence.  The  nature  of  the  evidence,  as  a  matter  of 
fact,  may  be  thus  stated :  It  had  long  been  believed  that  fer- 
mentation, decomposition,  ruiasm  and  contagion  were  caused 
by  processes  similar  or  identical  in  their  nature.  It  has  been 
proven  that  fermentation  and  decomposition  are  dependent 
upon  the  life  and  growth  of  certain  microscopic  organisms. 
Therefore,  miasmatic  and  contagious  diseases  are  caused  by 
3* 


44  THE   GEHM   THEORY   OF    DISEASE. 

microscopic  organisms.  This  kind  of  evidence  has  served  as 
the  basis  of  practice,  and  been  the  means  of  producing  im- 
provements in  the  management  of  wounds  particularly, 
greater  than  the  most  sanguine  theorist  could  have  expected 
thirty  years  ago. 

DIRECT  EXAMINATION. 

It  may  surprise  some  when  I  say  that  the  first  definite 
demonstration  of  micro-organisms  in  the  tissues  of  those  dying 
of  traumatic  disease  was  made  by  Rindfleisch,  in  1866.  Reck- 
]inghausen  and  Waldeyer  demonstrated  the  same  thing  about 
the  same  time.  Directly  afterward,  Birsch  Hirschfield  found, 
by  extended  examinations,  that  the  unhealthfulnessof  a  wound 
stood  in  direct  relation  to  the  numbers  of  spherical  bacteria 
found  in  the  pus  of  that  wound.  He  also  found  that  the 
blood  of  pysemic  patients  contained  bacteria  during  life. 

HIRSCHFIELD. 

Dr.  Birsch  Hirschfield,  on  examining  daily  the  pus  coming 
from  a  wound,  found  that,  with  the  ushering  in  of  the  first 
symptoms  of  pyaBmia,  the  pus  showed  a  corresponding  change, 
consisting  in  the  presence  of  micrococci,  either  in  pairs,  strings 
or  zooglea  (masses  of  micro-organisms,  of  whatever  kind,  often 
imbedded  in  a  gelatinous  mass,  the  latter  especially  when 
pyaemia  was  far  advanced  or  rapid  in  its  course),  and  in  an 
altered  appearance  of  the  pus  corpuscles,  which  were  finely 
granular,  of  less  definite  outline  and  lustre,  and  showed 
their  nuclei  very  distinctly,  without  the  addition  of  reagents. 

The  blood  of  such  patients  contained  similar  micrococci, 
and  its  white  corpuscles  had  undergone  a  change  very  similar 
to  that  of  the  pus  corpuscles.  He  sometimes  found  that  pus 
from  a  pya3mic  patient  would  contain  besides  these  a  quantity 
of  the  bacterium  termo  or  bacterium  lineola,  which  are  the 


NATUBE   OF   MIASM   AND   CONTAGION.  45 

common  bacteria  of  putrescent  matters,  while  micrococci, 
according  to  Cohn,  Klebs  and  Hirschfield,  are  not  to  be  con- 
sidered as  the  ferment  of  putrefaction.  (American  Journal, 
page  542,  Oct.  1873.) 

This  is  the  first  recognition  of  a  particular  form  of  micro- 
organism in  connection  with  a  given  condition  that  has  stood 
against  adverse  criticism. 

EVIDENCE  UNSATISFACTORY. 

Within  a  few  years  a  great  mass  of  such  evidence  as  this 
was  accumulated.  It  will  be  seen  at  once  that  this  kind  of 
evidence  is  fractional  and  not  conclusive.  It  shows  the 
presence  of  rnicro-organisms,  but  it  is  in  no  way  conclusive  as 
to  the  practical  effects  of  these  organisms  in  causing  any  given 
disease.  It  was  not  shown  that  the  disease  could  not  progress 
without  the  organisms. 

NATURE  OF  MIASM  AND  CONTAGION. 

During  this  time  a  theory  was  developed  for  the  explana- 
tion of  the  spread  of  certain  epidemic  diseases,  which  deserves 
mention,  not  only  for  its  intrinsic  merit,  but  for  the  reason 
that  it  has,  by  directing  thought  into  new  channels,  greatly 
enlarged  our  knowledge  of  the  cause  of  epidemics  and 
increased  our  means  of  defence  against  them.  We  have  here- 
tofore spoken  only  of  miasras  and  contagions. 

A  miasm,  according  to  the  germ  theory  of  disease,  is  an 
organism  developed,  under  certain  circumstances,  in  the  soil, 
decaying  vegetation,  marshes,  etc.,  of  certain  localities,  which 
can  enter  the  human  body  and  cause  disease,  but  cannot  grow 
a  second  time  in  the  body  of  another  person — at  least  does  not 
pass  from  the  sick  to  the  well — and  is,  therefore,  not  a  con- 
tagion. 

A  contagion  is  an  organism  whose  habitat,  by  nature  or 


46  THE   GERM   THEORY   OF   DISEASE. 

adaptation,  is  the  human  body,  and  the  spores  of  which  can 
pass  from  one  person  to  another,  either  by  contact  or  through 
the  air,  and  cause  disease  in  others. 

MIASMATIC  CONTAGION. 

A  third  class  partakes  of  the  nature  of  both,  but  differs 
from  both.  It  is  supposed  to  be  an  organism  which  has  one 
period  of  development  in  the  human  body  and  another  period 
without  the  human  body,  and  that  these  two  stages  are 
required  for  its  full  development.  Therefore,  such  diseases 
are  not  contagious;  they  cannot  pass  from  one  to  another 
until  they  have  found  a  suitable  soil  for  the  second  stage  of 
development  and  completed  their  spores.  When  this  has 
been  accomplished,  they  are  again  ready  for  the  production  of 
the  disease  in  man,  and  not  before. 

In  this  way  whole  regions  of  country  become  infected,  and 
persons  are  struck  down  with  the  disease  without  having  seen 
one  sick  of  it,  or  having  been  very  near  them.  Cholera,  Yellow 
Fever,  Typhoid  Fever,  and  various  other  diseases  belong  to 
this  class.  They  are  called  miasmatic  contagious  diseases. 

This  theory  is  not  based  upon  any  demonstration  yet  made, 
either  in  the  human  subject  or  upon  animals,  but  rests  upon 
the  known  life  history  of  certain  parasites  of  the  vegetable 
kingdom  and  circumstantial  evidence. 

Among  the  most  familiar  and  best  proven  of  the  vegetable 
parasites  which  run  through  this  kind  of  cycle,  is  the 
common  uredo  or  rust  on  wheat.  This  parasite  requires  two 
separate  growths  to  complete  its  spores.  Indeed,  it  seems  to 
have  a  double  set  of  spores.  The  spore  formed  on  wheat 
will  not  again  grow  upon  wheat,  but  will  grow  on  the  leaves 
of  certain  bushes,  especially  the  barberry  bush.  And  the 
spores  formed  on  these  bushes  will,  in  turn,  grow  on  wheat, 
thus  completing  its  cycle  of  existence. 


INFECTION   EXPERIMENTS.  47 

It  may  be  that  the  organisms  of  the  miasmatic  contagions 
require  free  oxygen  at  a  certain  stage  of  existence,  especially 
for  the  hatching  of  the  spores  formed  in  the  body,  after  which 
the  organism  itself  may  enter  the  body,  and  multiplying, 
cause  disease.  Some  examples  of  this  nature  have  been 
observed  in  organisms  inhabiting  putrid  substances.  The 
hatching  and  early  stages  of  existence  take  place  on  the 
surface,  but  the  after  life,  the  real  activity  of  the  organism, 
is  in  the  depths  of  the  mass,  away  from  free  oxygen.  Ac- 
cording to  this  idea  the  spores  passing  out  from  the  sick 
person  must  first  find  a  suitable  soil  for  hatching  and  the 
beginning  of  development,  before  they  are  ready  for  growth 
iii  the  human  body. 

The  efforts  already  made  on  this  theory,  for  the  prevention 
of  the  spread  of  epidemics,  have  been  sufficiently  successful 
to  furnish  an  additional  point  of  circumstantial  evidence  in 
favor  of  its  correctness. 

INFECTION  EXPERIMENTS. 

Turning  again  to  the  experimental  evidence,  we  find  that 
fragmentary  experimentation  has  taken  a  new  departure. 
Men  have  arisen  from  their  microscopes  and  begun  injecting 
the  bacterian  fluids  collected  from  wounds,  and  from  those 
dead  of  disease,  into  animals,  and  watching  their  effects. 
In  the  first  of  these,  the  animals  seemed  to  have  been  killed 
outright  by  the  amount  of  poisonous  material  injected,  and 
nothing  was  gained. 

Cose  and  Feltz  were  the  first  to  obtain  valuable  results. 
They  injected  a  small  quantity  of  blood  from  a  patient  just 
dead  of  puerperal  fever,  into  rabbits.  The  rabbits  sickened 
and  died  of  the  disease  induced.  The  blood  from  these  was 
injected  into  other  rabbits,  which  also  died  after  a  disease  of 
the  same  nature.  This  was  repeated  many  times,  always 


48  THE   GERM   THEORY   OF   DISEASE. 

with  the  same  results.  These  observations  were  repeated  and 
corroborated  by  a  very  large  number  of  observers,  within  a 
short  time,  and  Davaine  claims  that  after  twenty-five  successive 
transmissions,  he  found  one-trillionth  part  of  a  drop  of  blood 
sufficient  to  cause  the  disease  and  produce  death.  The  disease 
induced,  however,  was  pya3inia.  And  in  these  experiments 
this  remained  constant,  no  matter  -what  disease  the  patient 
had  from  whom  the  blood  was  taken. 

The  developments  of  this  series  of  experiments  were  very 
curious.  It  was  found  that  if  the  blood  was  filtered,  and  the 
serum  thus  obtained  injected,  sickness  and  death  resulted, 
but  no  pyaBinic  abscesses  occurred.  The  disease  induced  was 
different.  Now,  a  long  time  ago,  pya3mia  was  supposed  to  be 
caused  by  the  absorption  of  pus.  This  was  denied,  and  after 
much  discussion  of  the  subject,  there  was  an  effort  to  abandon 
this  term,  which  was  supposed  to  misrepresent  the  facts. 
Septicaemia  was  introduced  instead.  The  new  name,  how- 
ever, only  partially  succeeded  in  displacing  the  old  ;  for,  when 
septicaemia  occurred,  with  the  formation  of  abscesses,  it  was 
still  termed  pyaemia,  to  distinguish  this  accompaniment.  This 
series  of  experiments  seemed  to  demonstrate  that,  in  the  one 
case,  septicaBmia  is  caused  by  absorption  of  the  fluids  con- 
taminated by  the  effete  material  of  the  cocco-bacteria ;  while 
the  other,  pyremia,  is  caused  by  both  the  absorption  of  the 
fluids  and  the  entrance  of  the  cocco-bacteria. 

Recently,  however,  it  has  been  shown  that  each  .variety  is 
caused  by  a  special  form  of  micro-organism.  The  organism 
causing  septica3inia  being  so  minute  as  to  get  through  the 
filter,  had  escaped  the  earlier  investigators.  Dr.  Koch  of 
Berlin,  and  others,  have  clearly  demonstrated  that  the  fluids 
deprived  of  bacteria  will  produce  transient  poisoning ;  or  if 
in  sufficient  quantity,  will  kill;  demonstrating  its  poisonous 
nature. 


THIERSOH.  49 

With  this  study  came  a  much  greater  confidence  in  the 
germ  theory  on  the  part  of  many  zealous  observers.  Yet 
many  held  to  the  views  of  Liebig,  and  showed  that,  with  the 
exception  of  gaseous  ferments,  which  were  certainly  disproved, 
all  the  facts  could  be  accounted  for  on  the  molecular  motion, 
or  chemical  theory.  It  was  claimed  that  the  dried  remains 
of  decomposing  bodies  might  fly  about  in  the  air,  in  the  form 
of  fine  particles,  and  renew  their  effects  on  being  moistened, 
as  claimed  for  organic  germs,  and  be  kept  out  of  wounds,  or 
be  destroyed  by  the  same  means;  that  while  micro-organisms 
were  accompaniments,  they  were  not  a  cause  of  disease.  We 
will  give  the  views  held  by  some  of  the  great  men  of  the 
time,  as  showing  the  drift  of  the  thought  and  the  entangling 
of  views  that  have  occurred. 

THIERSCH. 

Professor  Thiersch,  writing  in  1875,  after  alluding  to  the 
success  of  the  Lister  method  of  treating  wounds,  and  sketching 
the  history  which  led  to  its  adoption,  seems  at  that  time 
not  to  have  been  fully  convinced  of  the  truth  of  the  germ 
theory  of  the  origin  of  septic  influences.  Granting  the  full 
force  of  Schroeder's  discovery,  he  thinks  it  still  possible  that 
the  power  of  generating  putrefaction  may  exist  in  the  fluid 
product  of  putrefaction  independently  of  organisms;  that  this 
power  may  be  retained  in  the  dry  remains  of  such  fluids, 
which  float  in  the  atmosphere,  and  be  filtered  out  by  cotton, 
the  same  as  claimed  for  organic  germs.  Consequently,  he 
then  considered  the  question  an  open  one,  as  to  whether  or 
not  putrefaction  can  progress  without  organic  germs.  He 
also  objects  to  the  deductions  from  these  experiments,  because 
albuminous  substances  are  always  changed  by  heat  in  the  ex- 
perimental flasks.  The  argument,  or  claim,  that  bacteria  are 
secondary  to  chemical  changes,  had  been  very  widely  held,  and 


50  THE   GERM   THEORY   OF   DISEASE. 

it  was  not  without  strong  grounds  in  its  favor.  In  Pasteur's 
flasks  the  organisms  were  always  transferred  to  fresh  flasks, 
together  with  a  small  quantity  of  the  fermented  fluid,  which, 
it  was  claimed,  prepared  the  way  for  the  development  of  the 
bacteria. 

LISTER. 

Mr.  Lister,  at  the  London  Congress,  Vol.  2,  page  371-2, 
relates  that  he  drew  blood,  with  antiseptic  precautions,  from  a 
vein  of  an  ox,  into  small,  purified  bottles,  and  allowed  it  to 
clot.  He  then  introduced  various  quantities  of  ordinary  tap- 
water  (London  hydrant  water)  into  the  different  bottles.  He 
was  surprised  to  find  that  even  eight  or  ten  drops  failed  to  set 
up  putrefaction  in  the  blood  serum,  while  the  one-hundredth 
part  of  a  drop  of  the  same  water  was  always  sufficient  to  set 
up  putrefaction  in  milk.  He  experimented  with  the  blood  of 
various  animals  with  the  same  results. 

He  found,  however,  that  if  the  blood  serum  was  diluted 
with  water  purified  by  boiling,  the  smallest  portion  of  tap- 
water  would  then  set  up  decomposition.  He  also  found  that 
putrefying  blood,  very  largely  diluted  with  water,  purified  by 
boiling,  did  not  readily  set  up  putrefaction,  while  the  smallest 
possible  amount  of  the  undiluted  putrefying  blood  set  up  the 
process  at  once.  Speaking  of  the  result,  he  says  :  "  How  it  is 
that  diffusion  of  the  bacteria  renders  them  incapable  of 
developing  in  the  serum,  I  do  not  profess  to  understand.  It 
may,  perhaps,  be,  that  when  the  bacteria  are  introduced 
directly  from  putrid  blood,  the  products  of  the  putrid  fer- 
mentation adhering  to  them  may  induce,  chemically,  an  altera- 
tion in  the  normal  quality  of  the  serum,  which,  when  thus 
impaired,  may  prove  amenable  to  the  nutritive  energies  of  the 
micro-organisms]  while,  conversely,  copious  ablution  with 
water  may  remove  from  them  the  associated  substances  which 
may  thus  act  as  their  pioneers.  The  view  might  be  otherwise 


DR.    SALMON.  51 

expressed  by  saying  that  the  bacteria,  per  se,  are  unable  to 
grow  in  normal  serum,  and  can  only  develop  in  the  liquid 
when  vitiated,  whether  by  the  addition  of  water  or  by  the 
action  of  small  quantities  of  the  acrid  products  of  decompo- 
sition. 

"  Or,  again,  it  seems  to  me  conceivable  that  the  normal 
serum  may  oppose  an  insuperable  obstacle  to  the  nutritive 
attractions  of  an  individual  bacterium,  but  that  this  may  be 
overcome  by  the  associated  attractions  of  several  of  the 
organisms  in  close  proximity,  after  the  analogy  of  the  more 
energetic  operation  of  a  concentrated  solution  of  a  chem- 
ical reagent.  But  whatever  be  the  explanation  the  fact  re- 
mains." 

I  give  the  first  statement  of  Mr.  Lister  as  the  strongest 
statement  of  the  view  against  the  primary  causative  effects  of 
bacteria  that  I  have  seen,  while  I  regard  the  second  as 
approaching  very  nearly  a  true  explanation  of  the  facts  in  the 
case.  I  will  refer  to  this  again. 

One  fact  Mr.  Lister  thinks  demonstrated  beyond  question. 
Pure  blood  resists  decomposition  under  circumstances  in  which 
very  many  other  substances  decompose,  and  that  a  blood  clot  is 
a  much  better  antiseptic  dressing  than  was  supposed.  Most 
forms  of  bacteria  must  be  grouped  together  in  some  numbers 
before  they  can  live  and  grow  in  blood ;  while  a  single  bac- 
terium lactis  detached  from  others  and  washed  with  purified 
water  will  be'sufficient  to  start  decomposition  in  milk. 

DE.   SALMON. 

The  idea  that  pathogenic  bacteria  must  be  grouped  together 
in  considerable  numbers  in  order  to  grow  in  the  blood  or 
tissue  of  animals,  has  recently  been  strongly  confirmed  by  the 
experiments  of  Dr.  Salmon  (see  Medical  Record,  April  7th, 
1883),  in  his  experiments  with  u  dilutions"  of  the  organisms 


52  THE   GERM   THEORY   OF   DISEASE. 

of  chicken  cholera.  This  experimenter  finds  that  dilutions 
of  the  fluid  containing  these  organisms  first  produce  a  mild 
type  of  the  disease  which  they  induce,  and  finally,  as  the 
dilution  is  increased,  fail  entirely  to  produce  an  effect,  although 
there  may  still  remain  in  the  drops  injected  a  number  of  the 
organisms.  He  believes  the  vital  energies  of  the  animal 
resist  the  growth  of  the  organisms,  and  that  numbers  are 
required  to  overcome  this.  We  will  allude  to  this  again. 

BILLROTH. 

Billroth,  in  the  course  of  his  inquiries  in  the  early  part  of 
the  sixth  decade,  published  in  1874,  came  to  the  conclusion 
that  organisms  were  present  in  the  human  body  and  in  the 
bodies  of  animals  in  a  state  of  health.  And  he  supposed 
that  in  case  of  injury  they  need  not  be  introduced  from  with- 
out in  order  to  develop  in  a  wound  and  produce  sepsis,  but 
that  they  may  come  from  the  tissues  beneath,  and  if  the  con- 
ditions of  the  wound  be  not  rendered  unfavorable  for  them, 
they  may  develop  sepsis.  Professor  Thiersch  seems  to  have 
attached  great  importance  to  this  view. 

In  the  same  publication,  Professor  Billroth  held,  also,  the 
view  that  bacteria  were  the  accompaniments  of  disease,  but 
denied  that  they  were  a  cause.  His  view  of  contagion  seems 
to  have  been  divided  somewhat  between  those  of  Liebig  and 
those  of  Beale  (vide  infra),  that  is,  he  seems  to  have  regarded 
both  these  as  operative  causes  or  modes  of  formation  of  con- 
tagious matters. 

In  his  introduction  to  a  report  on  surgery,  in  1876,  he  takes 
occasion  to  speak  of  this  subject  again,  and  seems  to  have  very 
materially  modified  his  views,  as  will  be  seen  by  the  following 
sentence,  which  I  quote:  "I  still  hesitate  to  accept  uncon- 
ditionally the  assurance  of  our  best  observers,  that  zymotic 
germs  have  much  to  do  with  the  causation  of  erysipelas, 


VIECHOW.  53 

diphtheritis,  septicaemia  and  pyaemia,  but  in  hospital  gan- 
grene there  appears  to  be  no  doubt  that  the  disease  is  so 
caused." 

Since  that  time  Billroth  has  fully  recognized  the  demon- 
strations of  Dr.  Koch.  (See  Belfield's  Lectures.) 

PROF.   THIERSCH. 

Prof.  Thiersch  relates  the  following  accidental  infection 
experiment:  "At  the  end  of  March,  1871,  the  recently 
finished  St.  Jacob's  Hospital  was  brought  into  use.  Some 
of  the  furniture  from  the  old  hospital  (which  was  not  in 
use  because  it  was  infected  with  hospital  gangrene),  was  piled 
up  in  one  of  the  courts.  After  some  weeks  it  had  disappeared, 
and  the  author  was  informed  that  it  had  been  removed  to 
a  more  fitting  place.  Two  days  later,  a  virulent  type  of 
hospital  gangrene  appeared  in  two  wards  (of  the  new  hospital), 
remote  from  each  other.  A  search  for  the  cause  of  this 
gangrene,  which  had  not  been  introduced  from  without,  ex- 
posed the  fact  that  the  old  infected  furniture  had  been  stowed 
in  two  basement  rooms,  from  which  these  two  wards  drew 
their  fresh  air." 

VIRCHOW. 

Prof.  Virchow  speaking  on  this  subject  at  the  International 
Congress  at  London,  especially  of  the  claim  so  often  made 
that  micro-organisms  could  only  exist  in  diseased  organs,  that 
they  were  scavengers,  which  only  attacked  the  dead  or  dying, 
said  he  thought  the  view  was  one-sided.  It  was  necessary 
to  distinguish  between  different  forms  of  these  organisms. 
Some  very  virulent  organisms  can  multiply  anywhere,  in  all 
tissues  and  at  all  times. 

"The  bacillus  anthracis  had  no  need  of  diseased  tissues. 
It  is  vigorous  enough  to  destroy  any  tissue,  and  will  develop 
itself  in  a  short  time,  from  the  point  of  introduction,  into  a 


54  THE   GEKM   THEORY   OF   DISEASE. 

large  focus  of  disease.  So  with  diphtheria.  It  is  not  neces- 
sary for  any  diseased  part  to  exist  before  the  disease  com- 
mences; that  is,  the  organism  finds  its  way  into  healthy 
parts." 

"  The  action,  then,  of  the  virulent  organisms  is  very  differ- 
ent, and  it  is  more  philosophical  to  explain  the  facts  in  this 
way,  than  to  refer  the  differences  to  .the  mode  of  action  of 
the  parts." 

"  Part  of  them  (kinds)  will  penetrate  into  the  interior  of 
cells,  and  there  multiply,  while  the  cells  will  perish,  destroyed 
by  the  evolution  of  the  parasitic  organism." 

In  other  cases  (kinds)  the  organisms  pass  between  the  cell 
elements  into  the  interstices  of  the  tissues,  or  into  the  inter- 
cellular substance.  In  this  case  the  action  of  the  organisms 
upon  the  cells  is  not  direct.  The  cells  are  only  affected  by 
some  matter  secreted  by  the  organisms,  or  by  some  chemical 
substance  produced  by  the  action  of  the  latter  upon  the  fluids 
of  the  body. 

PKOF.   KLEBS,  OF   PRAGUE. 

Prof.  Klebs,  of  Prague,  a  worker  in  this  field,  of  great 
ability,  in  his  address  upon  this  subject  at  the  London 
Medical  Congress,  discussed  the  views  of  Bastiau,  of  the 
spontaneous  generation  of  organisms;  and  in  summing  up, 
says  that  "  since  it  is  abundantly  shown,  by  observation  which 
is  trustworthy  and  reliable,  that  the  material  cause  of  disease 
is  introduced  from  without,  therefore,  the  subject  of  spon- 
taneous generation  has  no  weight  in  this  discussion." 

"  Those  organisms  produced  in  the  body,  or  those  normally 
inhabiting  healthy  tissues,  if  such  were  proven  to  exist,  could 
not  be  regarded  as  a  cause  of  disease.  Only  one  possibility 
can  here  be  entertained.  Can  the  organisms  ordinarily  exist- 
ing in  the  healthy  body  (if  such  there  be,  which  Klebs  denies) 


VOLKMAN.  55 

be  so  changed,  on  account  of  change  in  the  fluids  which  they 
inhabit,  that  they  may  become  a  cause  of  disease.  No  dis- 
ease has  been  shown  to  arise  under  conditions  which  would 
make  this  seem  probable."  Continuing,  he  says,  "We  may 
proceed  from  this  proposition  as  the  basis  of  future  inquiry." 
"  Specific  diseases  are  caused  only  by  specific  organisms." 
"  The  question  now  arises,  whether  specific  differences  of  a 
morphological  nature,  which  remain  constant,  can  be  shown 
to  exist  in  such  organisms,  so  that,  beforehand,  their  nature 
can  be  shown  by  their  forms."  "  It  is  possible  that  the 
specific  effects  may  be  due  to  fine  chemical  differences  in  the 
working  of  these  organisms."  "  But,  happily,  even  here  the 
general  law  of  nature  holds  good,  that  difference  of  perform- 
ance is  represented  by  difference  of  form,  and  that  within  the 
same  form  lines  there  are  different  grades,  only,  of  perform- 
ance or  capability." 

Prof.  Klebs  thinks  that  the  knowledge  already  attained  is 
sufficient  to  demonstrate  that  the  forms  of  the  organisms 
causing  disease  do  remain  constant,  and  produce  the  same 
phenomena  and  nothing  else,  under  given  conditions.  -  He 
attempts  a  classification,  but  admits  that  our  knowledge  is 
not  yet  sufficient  for  a  satisfactory  basis. 

VOLKMAN. 

Prof.  Volkman,  of  Halle  (London  Congress,  vol.  ii,  page 
362),  took  strong  grounds  in  favor  of  the  germ  theory.  He 
says,  "We  know  of  no  suppuration  which  does  not  depend 
on  the  influence  of  organic  ferments.  ...  In  the  worst  con- 
stitutions, and  with  the  most  disordered  state  of  health,  no 
suppuration  takes  place  if  septic  infection  is  prevented.  .  .  . 
If  we  could  completely  exclude  all  organic  ferments,  the 
largest  open  wounds  and  the  most  extensive  loss  of  tissue 
would  heal  without  suppuration." 


56  THE   GERM    THEORY   OF   DISEASE. 

LISTER'S  REPLY. 

This  was  evidently  regarded  by  Mr.  Lister  as  a  very  ex- 
treme view.  And  he  replied,  speaking  very  strongly  against 
the  conclusions  reached  by  Prof.  Volkman,  Klebs,  and  some 
others.  He  says,  "But,  gentlemen,  while  I  am  more  than 
ever  convinced  of  the  relations  of  micro-organisms  to  disease 
processes  in  wounds,  I  propose  to  utter,  this  morning,  what 
seems  to  me  to  be  a  needed  note  of  warning  against  a  tend- 
ency to  exaggeration  in  this  direction.  This  exaggeration, 
if  such  there  be,  is  largely  due  to  the  success  of  the  anti- 
septic treatment." 

After  speaking  of  the  certain  success  of  the  antiseptic 
treatment  of  wounds,  and  the  banishment  of  septicaBinia, 
pyaBtnia,  hospital  gangrene,  etc.,  he  says,  "  Such  success  pro- 
ceeding from  a  mode  of  treatment  designed  especially  to 
exclude  bacteria,  may  suggest  that  all  inflammations  are  due 
to  micro-organisms,  and  that  suppuration,  acute  or  chronic, 
is  always  due  to  similar  agencies.  Gentlemen,  I  believe  this 
to  be  a  very  exaggerated  view  of  the  matter,  and  a  view 
which  may  tend  to  have  a  serious  influence  on  our  practice." 

"  For  example,  if  we  believe  inflammations  are  due  only 
to  the  invasions  of  microscopic  organisms,  to  what  purpose 
do  we  employ  counter-irritation." 

Mr.  Lister  then  goes  on  to  show  that  inflammation  does 
arise,  in  very  many  instances,  without  the  aid  of  micro-organ- 
isms, and  from  a  variety  of  causes,  both  in  wounds  and  sepa- 
rate from  wounds.  That  abscesses  form,  and  pus  forms,  in 
many  instances,  under  circumstances  that  exclude  bacteria. 
Also,  that  strict  search  has  shown  the  pus,  under  such  cir- 
cumstances, to  be  free  from  bacteria. 


THIRD  LECTURE. 

BEALE. 

It  will  not  be  out  of  place  to  notice  here  the  peculiar  views 
of  Dr.  Lionel  S.  Beale. 

In  a  work  published  in  1870,  entitled,  "Disease  Germs; 
their  Nature  and  Origin,"  Dr.  Beale  holds  a  view  of  this 
subject  different  from  the  more  generally  accepted  theory,  and 
differing  entirely  from  both  Schwan  and  Liebig  as  to  the 
nature  of  contagions.  We  should  say,  however,  that  this  view 
was  not  entirely  original  with  Dr.  Beale,  but  he  has  given  the 
most  perfect  exposition  of  it. 

In  respect  to  bacteria,  he  regards  them  as  accidental  accom- 
paniments of  disease ;  their  home  is  among  dead  matter, 
having  nothing  to  do  with  the  living.  Further,  they  are  of 
no  distinct  species  or  form ;  a  spore  may  produce  this  or  that 
form,  according  to  its  environment,  and  nothing  can  be  pre- 
dicated of  the  action  of  any  particular  form.  They  are 
scavengers  only. 

The  action  of  a  contagion  is  not  a  fermentative  process  in 
any  respect,  either  in  accordance  with  Liebig  and  the  chemists, 
or  in  accordance  with  the  views  of  Schwan  and  Pasteur.  All 
the  facts  he  thinks  susceptible  of  a  different  explanation. 

Dr.  Beale  regards  disease  germs  as  being  derived  directly 
from  the  human  tissues  by  a  process  of  physiological  degrada- 
tion— by  a  metamorphosis  of  functional  activity — without 
there  being  necessarily  any  change  of  form  from  the  normal 
cell  or  bioplasm.  This  is  the  bioplasm  theory  of  contagion. 
It  has  also  been  termed  the  amoaboid  theory. 

Dr.  Beale  believes  contagious  disease  germs  to  consist  of 

57 


58  THE   GERM   THEORY   OF    DISEASE. 

outgrowths  from  the  white  corpuscles  of  the  normal  blood, 
excited  by  germs  of  a  similar  nature.  This  outgrowth  occurs 
in  successive  changes  in  the  physiological  activity  of  the  bio- 
plasm of  each  successive  globule  of  living  matter,  as  new 
globules  are  given  off  from  the  parent  globule,  uutil  the  type 
of  the  exciter  of  the  change  has  been  reached  more  or  less  per- 
fectly. After  these  changes  have  been  induced,  and  have  run 
their  course,  many  of  these  bioplasts  die  and  are  eliminated 
from  the  system.  But  very  many  are  eliminated  in  the  living 
state,  and  the  person  or  animal,  if  it  has  been  able  to  with- 
stand the  attack,  returns  to  a  state  of  health. 

The  germs  eliminated  in  the  living  state  have  acquired  a 
wonderful  tenacity  of  life,  and  are  capable  of  living  for  a  very 
considerable  time  in  the  atmosphere.  They  have  the  power 
of  entering  into  the  circulation  of  another  animal  by  way  of 
mucous  membranes  and  otherwise.  And  when  so  entered,  they 
induce  precisely  the  same  changes  in  the  blood  as  before 
described. 

This  is  an  extension  to  the  contagious  diseases,  with  some 
change  of  form,  of  the  theory  now  generally  held  as  to  the 
nature  of  the  formation  of  neoplasms,  or  new  growths  in  the 
form  of  tumors,  such  as  cancer,  sarcoma,  etc. 

These  are  regarded  as  changes  in  the  physiological  character 
of  the  cells  of  the  part,  by  which  they  take  on  new  properties 
resulting  in  abnormal  proliferation  of  cells  with  like  charac- 
teristics. These  cells,  when  transplanted  to  other  animals, 
will,  if  the  conditions  be  favorable  for  them,  grow  and  mani- 
fest all  their  acquired  physiological  characters.  In  this  way, 
epithelial  cancer  may  be  transferred  from  man  to  the  animals, 
or  from  person  to  person,  perhaps,  as  readily  as  syphilis  from, 
person  to  person,  except  that  the  cancer  cells  must  be  actually 
grafted  into  the  second  person. 

Moreover,  it   is  generally  recognized  that  the  infiltration 


BEALE.  59 

which  occurs  so  generally  in  carcinoma  is  due  to  the  wander- 
ing of  young  cells  or  bioplasts  from  the  seat  of  the  tumor, 
which  have,  through  a  process  of  physiological  degradation, 
acquired  new  properties  by  which  they  are  enabled  to  initiate 
a  new  focus  of  disease  wherever  they  may  lodge  in  the  tissue. 
These  are  found  to  wander  along  the  course  of  the  lymph 
streams  especially,  and  to  a  lesser  extent  along  the  blood 
streams.  There  is  also  a  certain  wandering  among  the 
neighboring  tissues,  infiltration. 

Such  diseases,  however,  are  never  contagious,  in  the  ordinary 
sense  of  that  term,  and  such  cells  do  not  acquire  any  power  of 
continued  life  when  isolated  from  the  animal  economy. 

In  arguing  the  point,  Dr.  Beale  does  not  insist  that  in  each 
individual  case  the  white  corpuscles  of  the  blood  must  pro- 
duce the  germs  of  contagion.  f<  For,"  he  says,  "  the  facts  may 
be  accounted  for  solely  by  the  proliferation  and  growth  of  the 
acquired  germs  or  those  that  have  been  implanted  from  with- 
out. But,"  he  says,  "  the  fact  that  living  matter  of  the  blood 
of  one  individual  will  live  in  the  blood  vessels  of  another, 
that  the  skin,  periosteum  and  other  tissues  may  be  trans- 
planted and  grafted,  prepare  us  for  the  remarkable  circum- 
stance, demonstrated  by  experiment,  that  living  pus  bioplasts, 
which  have,  indeed,  been  derived  from  normal  bioplasm,  may 
traverse  long  distances,  free  and  independent,  and  then,  gain- 
ing access  to  other  organisms,  may  live  and  grow  and  multiply 
in  them,  and  establish  changes  of  the  same  kind  as  those  which 
were  taking  place  at  the  seat  of  their  origin." 

In  speaking  of  the  first  origin  of  contagions,  he  says,  "It  is 
possible  that  the  exceedingly  minute  living  particles  which 
constitute  the  (  contagium '  of  contagious  diseases  may  be  the 
degraded  offspring  of  some  kind  of  normal  living  matter  or 
bioplasm,  which  originally  possessed  comparatively  exalted 

tissue-forming,  or  other  formative  powers The 

4 


60  THE   GERM   THEORY   OF   DISEASE. 

phenomena  which  occasion  the  formation  of  ordinary  pus, 
may,  if  they  continue  to  occur  for  a  long  period  of  time, 
determine  the  development  of  a  specific  pus,  which  has  still 
more  marvelous  powers  of  vitality.  So,  I  think,  it  may 
reasonably  be  argued  that  if  the  ordinary  feverish  state  be 
prolonged  for  a  considerable  time,  and  be  severe  in  degree,  it 
is  likely  that  the  bioplasm  in  the  blood,  collected  in  the 
capillaries,  may  give  origin  to  bioplasm  with  marvelously 
increased  power  of  retaining  its  vitality  and  of  growing  and 
multiplying.  The  particles  of  this  making  their  way  through 
the  vessels  and  escaping  may  live  for  a  considerable  time,  and 
having  entered  the  blood  of  another  person  may  excite  in  it 
the  changes  which  accompanied  its  own  development." 

"  Finally,"  Dr.  Beale  says,  "  it  is  not  probable  that  disease 
germs  have  sprung  from  insects,  or  animalcules,  or  any  kind 
of  vegetable  organisms ;  neither  have  they  originated  in  the 
external  world  and  seized  upon  man  ;  but  they  have  been  de- 
rived by  direct  descent  from  the  normal  living  bioplasm  of 
the  organism.  They  have  originated  in  man,  and  if  man  is 
not,  indeed,  responsible  for  their  origin,'he  has  certainly  him- 
self imposed  the  conditions  favorable  to  their  production  and 
dissemination." 

It  is  worthy  of  note  that  the  experimental  proof  upon 
which  Dr.  Beale  relies  for  his  theory  is  similar  to  that  upon 
which  others  have  relied  for  proof  that  bacteria  cause  disease, 
namely,  injection  by  pus  and  fluids  from  the  tissues,  and 
observations  of  the  transmission  of  contagions,  the  means  by 
which  they  may  be  prevented,  etc.  He  does  not  pretend  that 
the  character  of  such  contagious  bioplasm  can  be  determined 
by  microscopic  study,  but  on  the  contrary,  distinctly  asserts 
that  it  cannot,  and  further,  that  the  study  of  the  subject  gives 
no  hope  whatever  of  demonstration  by  this  mode  of  inquiry; 
fur  the  reason  that  the  bioplasmic  forms  give  no  indication 


BACILLUS   ANTHRAX.  61 

whatever  as  to  the  character  of  their  physiological  activity. 
As  a  theory  it  is  very  interesting,  and  is  certainly  very  in- 
genious, and  at  the  same  time  quite  plausible.  It  has,  how- 
ever, made  but  little  impression  upon  the  thought  of  the  world, 
and  is  now  strictly  limited  to  those  diseases  characterized  by 
new  growths  of  tissue,  by  a  great  majority  of  the  prominent 
thinkers  of  the  profession. 

In  the  discussion  of  this  subject  at  the  International 
Congress,  this  theory,  as  applied  to  contagious  diseases,  was 
mentioned  but  once.  Dr.  Richardson,  of  London,  held  views 
almost  identical  with  those  of  Dr.  Beale.  (See  American 
Journal  of  the  Medical  Sciences  for  October,  1875,  page  516, 
for  Dr.  Richardson's  views.) 

Dr.  John  Bell  holds  the  same  views.  (See  Half-yearly 
Compendium,  January,  1872,  page  112.)  Also  Prof.  Crooks 
and  many  other  important  persons  ;  indeed,  this  seems  to  have 
been  the  most  prevalent  view  in  England  during  the  eighth 
decade  of  this  century.  Lister's  success,  however,  swerved 
the  thought  of  Englishmen  to  the  theories  of  Schwan  and 
Pasteur. 

BACILLUS  ANTHRAX. 

While  the  experiments  detailed  in  our  last  lecture  were 
being  carried  on  mostly  in  Germany,  Pasteur  was  still  busy 
in  France  with  his  flask  cultivations.  Having  demonstrated 
the  nature  of  the  ordinary  ferments  by  pure  cultivations 
(fractional  cultivations  as  they  came  to  be  called,  the  develop- 
ment of  one  species  out  of  many),  he  turned  his  attention  to 
contagious  diseases,  and  finally  hit  upon  some  brilliant  re- 
sults. The  most  widely  known  and  best  proven  of  these  is 
the  isolation  of  the  bacillus  anthrax,  the  contagium  of  that 
dread  disease  which  has  made  such  havoc  among  sheep  and 
cattle  in  many  parts  of  Europe,  and  also  has  been  many 
times  epidemic  among  men  with  deadly  effect.  He  obtained 


62  THE   GERM   THEORY   OF   DISEASE. 

this  bacillus  entirely  pure,  and  succeeded  in  causing  the  dis- 
ease in  animals  by  inoculating  them  with  it,  after  the  fiftieth, 
on  to  the  one  hundred  and  fiftieth  generation,  grown  pure  in 
his  flasks.  The  whole  life  history  of  the  organism  has  been 
made  out,  and  is  now  substantially  confirmed  by  a  large 
number  of  separate  observers.  Indeed,  this  bacillus  is  re- 
cognized on  sight  by  observers  in  this  field  of  work  every- 
where. It  can  be  bottled  up  and  sent  to  any  part  of  the  world, 
like  vaccine  virus,  and  produces  the  disease  in  regions  where 
it  was  unknown,  just  as  readily  as  at  home.  This  would 
seem  to  be  a  complete  demonstration  of  the  germ  theory. 
Yet  strangely  enough  its  acceptance  as  such  has  been  received 
with  extreme  caution.  That  M.  Pasteur  had  the  virus  of 
anthrax,  no  one  could  doubt,  but  was  it  the  bacillus,  or  was 
it  contained  in  some  other  form  in  the  culture  medium,  and 
thus  carried  from  flask  to  flask.  It  was  still  claimed  that 
the  molecular  motion  described  by  Liebig  had  not  been 
eliminated. 

KOCH. 

We  have  now  to  notice  a  class  of  experiments  still  more 
conclusive  than  any  preceding  ones,  and  which  are  as  yet 
unexcelled.  But  it  is  first  necessary  to  notice  the  manner  in 
which  they  were  approached.  These  are  by  Dr.  Koch,  of 
Berlin,  working  under  the  auspices  of  the  Prussian  govern- 
ment. 

This  brilliant  experimentalist  has  been  very  fortunate  in 
his  endeavors  to  devise  more  perfect  means  of  recognizing 
very  minute  organisms  with  certainty ;  and  of  isolating  them 
by  pure  cultures.  One  of  his  first  and  most  important  feats 
was  the  devising  of  a  plan  of  staining  these  organisms,  by 
which  he  was  enabled  to  practically  isolate  them  from  the 
animal  tissues.  By  his  plan  of  aniline  staining  he  succeeded 
in  obtaining  the  organisms  colored  a  dark  blue,  while  the 


KOCH.  63 

tissues  were  rendered  transparent.  So  completely  was  this 
accomplished,  that  the  animal  tissues  were  practically  gotten 
out  of  the  way  of  the  observation  of  the  organisms.  His 
plans  have  now  been  tried  by  a  large  number  of  investigators, 
and  have  stood  the  test  of  adverse  criticism.  By  this  new 
plan  of  work  it  was  soon  demonstrated  that  the  normal  tissues 
of  men  and  animals  are  entirely  free  from  these  organisms ; 
and  that  the  bodies  before  thought  to  be  such  by  Billroth, 
Thiersch,  and  many  others,  were,  in  fact,  the  granular  con- 
stituents of  the  blood.  Billroth  and  others,  after  experiment- 
ing with  the  new  process,  have  fully  admitted  the  demonstra- 
tion. And  the  point  may  be  considered  as  fully  settled. 

Dr.  Koch  now  began  his  work  by  the  then  common  plan 
of  injecting  septic  blood  into  the  tissues  of  animals.  At  first, 
his  results  were  similar  to  those  common  with  this  mode  of 
experimentation.  Too  much  of  the  material  killed,  by  direct 
poisoning,  while  a  small  amount  induced  disease.  Even  the 
slightest  scratch  of  a  blade  that  had  been  dipped  into  the 
blood  of  the  dead  house  mouse  on  which  he  was  experimenting 
produced  the  disease  and  death,  in  the  usual  time,  upon  a 
second  mouse,  i.  e.,  from  forty  to  sixty  hours.  The  organism 
found  in  the  blood  of  the  dead  animals  was  a  very  minute 
bacillus,  which  remained  constant  and  pure.  An  effort,  during 
these  experiments,  to  inoculate  field  mice  with  the  bacillus 
cultivated  in  this  way  in  the  house  mice,  failed  entirely. 
They  proved  to  be  in  no  wise  susceptible  to  the  disease. 

Now,  Dr.  Koch,  in  his  examinations  of  the  tissues  of  the 
dead  house  mouse  of  the  original  experiment,  had  found  at 
the  point  of  injection  an  organism  entirely  different  from 
that  found  in  the  blood,  and  which  he  got  rid  of  in  the  injec- 
tions made  afterward  ;  having  obtained  these  in  as  perfect 
isolation  as  he  could,  by  the  means  at  that  time  devised,  and 
tried  them  on  the  field  mice,  he  was  surprised  to  find  that 


64  THE   GERM   THEORY   OF   DISEASE. 

they  produced  a  different  disease  entirely,  which  was  not  seen 
in  the  experiments  on  the  house  mouse,  for  the  reason  that  it 
was  killed  by  the  first  and  more  quickly  acting  organism,  be- 
fore the  second  had  time  to  produce  its  effects.  This  new 
disease  ran  a  course  identical  with  the  dreaded  hospital  gan- 
grene. The  organism  did  not  pass  into  the  circulation  at  all. 
It  spread  by  its  growth  merely,  and  destroyed  all  tissues  with 
which  it  came  in  contact,  until  vital  organs  were  reached  and 
the  animal  destroyed.  The  parasite  was  found  only  in  the 
diseased  tissue,  never  in  the  blood. 

Dr.  Koch  says  of  this :  "  These  appearances  lead  us  to  the 
conclusion  that  the  action  of  these  micrococci  in  causing  the 
gangrene  is  somewhat  as  follows :  Introduced  by  inoculation 
into  living  animal  tissues,  they  multiply,  and  as  a  part  of 
their  vegetative  process,  they  excrete  soluble  substances  which 
get  into  the  surrounding  tissues  by  diffusion.  When  greatly 
concentrated,  as  in  the  neighborhood  of  the  micrococci,  this 
product. of  the  organisms  has  such  a  deleterious  effect  on  the 
cells  that  these  perish  and  finally  completely  disappear.  At 
a  greater  distance  from  the  micrococci  the  poison  becomes 
more  diluted  and  acts  less  intensely,  only  producing  inflam- 
mation and  accumulation  of  lymph  corpuscles.  Thus  it 
happens  that  the  micrococci  are  always  found  in  the  gan- 
grenous tissue,  and  that,  in  extending,  they  are  preceded  by  a 
wall  of  nuclei,  which  constantly  melts  down  on  the  side 
directed  towards  them,  while,  on  the  opposite  side  it  is  as  con- 
stantly renewed  by  lymph  corpuscles  deposited  afresh." 

Inoculation  with  the  juices  of  the  dead  tissue  never  failed 
to  induce  the  disease.  Inoculation  with  the  blood  did  not 
induce  the  disease  in  any  case.  When  the  house  mouse  was 
inoculated  with  this  material,  the  disease  induced  was  pre- 
cisely the  same  as  in  the  field  mouse.  Thus,  these  two  forms 
of  organism,  one  a  very  minute  bacillus,  the  bacillus  septicus, 


KOCH.  65 

the  other  a  chain-like  cocco-bacterium,  were  isolated,  and  after- 
ward obtained  entirely  pure  by  culture  on  dry  slides — a  plan 
presently  to  be  described. 

Why  the  field  mice  were  insusceptible  to  the  disease  so 
readily  induced  in  the  house  mouse,  remains  a  profound  mys- 
tery. Yet  it  is  in  accord  with  facts  that  are  continually 
coming  to  light.  It  is  a  well-known  fact  that  certain  persons 
resist  the  contagium  of  smallpox,  while  others  around  them 
are  struck  down;  and  the  same  is  true  of  every  other  con- 
ta'nous  disease.  It  is  also  a  well-known  fact  that  some 

o 

classes  of  animals  are  insusceptible  to  certain  diseases  common 
to  other  animals  nearly  related  to  them.  It  would  seem  that 
the  organism  inducing  the  particular  disease  does  not  find  in 
this  or  that  animal  a  suitable  habitat,  but  why,  is  unknown. 

As  I  have  said,  this  class  of  experiments  had  been  made  by 
many  before  Dr.  Koch ;  but  he  had  developed  a  distinctive 
feature.  He  had  demonstrated  that  the  same  tissues  or  fluids 
might  contain  germs,  which,  when  separated,  would  produce 
separate  and  distinct  processes  of  disease.  Heretofore,  as  has 
been  said,  this  class  of  experiments  had  only  succeeded  in  pro- 
ducing septicaBmia  and  pyaemia,  which  were  regarded  as  parts 
of  the  same  process.  And  this  result  was  induced,  no  matter 
what  the  disease  with  which  the  patient  from  whom  the 
material  was  obtained,  may  have  died  ;  results  very  confusing 
to  those  who  believed  that  different  diseases  are  induced  by 
distinct  and  separate  germs. 

We  have  already  spoken  of  the  fact  that  these  results  were 
very  nearly  identical  with  ordinary  blood  poisoning  from 
wounds.  Now  in  the  discussion  of  Dr.  Koch's  experiments 
a  new  thought  was  developed.  The  substances  injected  were 
all  contaminated  with  septic  germs ;  and  these  virulent  germs 
had  killed  the  animals  experimented  upon,  before  other  and 
slower  acting  germs  had  time  to  produce  their  results.  The 


66  THE   GERM   THEORY    OF   DISEASE. 

more  the  matter  was  discussed,  the  more  certain  it  seemed 
that  this  had  been  demonstrated.  One  point  of  vast  import 
had  been  attained ;  and  now  the  experimentation  must  pro- 
ceed from  the  new  basis.  Inoculation  must  be  with  pure 
virus  of  some  particular  disease ;  not  a  supposed  virus  mixed 
with  various  germs.  Otherwise  nothing  distinctive  could  be 
expected. 

As  we  have  said,  Pasteur  had  gained  a  most  happy  result 
from  his  flask  cultures,  in  the  isolation  of  the  bacillus  anthrax. 
But  it  had  cost  an  immense  amount  of  labor,  and  shown  that 
the  results  were  very  uncertain  at  best.  Besides,  there  was  a 
serious  objection  urged  against  flask  cultures,  in  that  small 
portions  of  the  fermenting  fluid  were  always  transferred  to 
the  flasks  with  the  organisms.  The  anti-vitalists  claimed 
that  the  molecular  motion,  poison  or  chemical  ferments  were 
carried  over  by  the  small  portion  of  fermenting  fluid  trans- 
ferred, and  that  where  there  were  fermentable  fluids,  this 
power  would  be  propagated.  It  is  evident  that  this  argu- 
ment carried  with  it  much  force,  for  such  men  as  Prof.  Bill- 
roth,  Prof.  Thiersch,  and  others  of  the  great  medical  men 
of  the  world,  still  considered  this  argument  a  valid  one, 
which  still  placed  the  causative  effect  of  micro-organisms  in 
doubt. 

Therefore  other  means  of  cultivation  were  earnestly  sought. 
Dr.  Koch,  of  Berlin,  was  again  the  successful  man.  He  de- 
vised and  brought  into  successful  operation  the  Dry  Slide 
Cultivation,  by  which  the  particular  organism  could  be  watched 
during  its  entire  development,  by  the  eye  of  the  experimenter, 
so  that  it  could  be  seen,  at  any  stage  of  the  process,  whether 
or  not  the  cultivation  was  contaminated  by  other  organisms 
than  the  one  desired. 

The  plan  was  this.  Suitable  material  to  serve  as  food,  or 
soil,  for  the  sustenance  of  the  organism  was  mixed  with 


KOCH.  67 

albumen  and  sterilized  by  heat.  This  was  carefully  reduced 
to  a  jelly  that  would  solidify  on  cooling,  and  spread  in  a  thin 
layer  on  glass  slides  suitable  for  microscopic  examination. 
When  the  slides  were  thus  prepared,  a  needle  was  dipped  in 
the  fluid  containing  the  organisms  and  drawn  quickly  across 
the  surface  of  the  prepared  culture  medium,  in  such  a  way  as 
to  distribute  the  few  that  adhered  to  the  needle,  along  the 
line  of  its  track.  This  preparation  was  then  sealed  up,  or 
otherwise  protected  from  contamination,  and  kept  at  a  suitable 
temperature  for  the  growth  of  the  organisms,  and  occasion- 
ally examined  with  the  microscope.  It  was  found  that  the 
organisms  grew  well  on  such  soil  or  food ;  also,  that  it  re- 
quired the  utmost  care  to  prevent  contaminations.  These, 
however,  could  be  detected  by  microscopic  examination,  and, 
whenever  found,  rejected.  It  was  also  found  that  the  differ- 
ent organisms  present  in  a  fluid  could  be  separated  by  this 
method  of  culture;  for  in  drawing  the  needle  point  along 
the  surface  of  the  solidified  jelly,  the  organisms  would  often 
be  distributed  singly,  and  would  develop  in  little  groups  that 
could  be  seen  by  the  naked  eye.  The  characters  of  each  could 
be  determined  by  the  microscope.  These  were  generally  found 
in  the  form  of  little  flakes  on  the  surface  of  the  jelly,  and 
each  could  be  detached  with  a  needle  and  conveyed  to  another 
slide,  or  when  desired,  to  a  culture  fluid,  and  kept  pure. 
From  these  pure  growths  the  organisms  are  transplanted  to 
other  slides,  or  culture  fluids,  at  will,  and  for  any  number  of 
generations,  and  kept  absolutely  pure.  Inoculations  were 
made  with  these  pure  cultivations;  and  such  inoculations 
were  found  constant  in  their  effects,  whether  taken  from  the 
fifth  or  the  one  hundredth  generation. 

By  this  process,  it  is  believed  that  the  difficulty  heretofore 
existing,  as  to  the  exclusion  of  a  possible  chemical  ferment, 
has  been  incontestably  overcome.  The  phenomena  are  watched 

A* 


68  THE   GERM    THEORY    OF    DISEASE. 

by  the  microscope,  and  the  growth  of  the  organisms  is  all 
that  is  seen.  This,  when  carried  on  from  slide  to  slide,  for 
several  generations,  must  disconnect  the  organisms  from  any 
possible  following  of  a  chemical  ferment.  So  palpable  is  this 
demonstration  that  Billroth,  Thiersch,  and  many  others,  who 
had  maintained  a  position  of  skepticism,  have  fully  acknow- 
ledged it. 

By  use  of  these  pure  dry  cultivations,  Dr.  Koch  proved  his 
former  experiments.  He  also  obtained  and  cultivated  the 
bacillus  anthrax  by  this  mode;  the  bacillus  of  erysipelas,  the 
bacillus  of  leprosy,  and  some  others  of  less  note;  and  last 
of  all,  that  is  as  yet  definitely  announced,  the  bacillus  of 
tuberculosis. 

RESULTS. 

It  will  be  seen  that  this  work  is  only  just  begun.  While 
we  have  circumstantial  evidence  of  the  existence  of  very  many 
disease  germs,  only  a  few  have  been  positively  demonstrated 
by  isolation  and  pure  cultivations,  followed  by  inoculations 
and  the  production  of  specific  forms  of  disease.  These  are  the 

Bacillus  anthrax. 

Organism  of  chicken  cholera. 

Bacillus  of  septicaemia. 

Micrococcus  of  pyaBmia. 

Cocco-bacterium  of  gangrene. 

Bacillus  of  erysipelas. 

Bacillus  of  tuberculosis. 

Bacillus  of  leprosy. 

Spirillum  Obermeiri,  the  virus  of  relapsing  fever. 
Besides  these,  there  are  some  others  not  so  certainly  demon- 
strated. A  considerable  number  of  organisms  are  now  pretty 
well  known  by  their  continued  association  with  a  particular 
form  of  disease,  but  have  not  yet  been  demonstrated  by  pure 
cultivations  and  inoculations.  The  task  of  isolating  one  of 


THE   EVIDENCE.  69 

these  forms,  to  begin  with,  is  generally  extremely  difficult,  for 
it  is  often  associated  with  other  forms,  most  of  which  have  no 
disease-producing  power,  and  the  experimenter  generally  has 
no  guide  as  to  which  is  the  one  wanted  until  he  has  carried 
it  through  the  cultivations  and  has  made  some  inoculations. 
In  many  of  the  diseases  he  is  met  with  another  difficulty, 
which  he  often  has  no  guide  whatever  in  surmounting,  in  the 
fact  that  he  does  not  know  what  animals  are  susceptible  to  the 
disease.  A  considerable  number  of  diseases  in  men  have  not 
been  known  among  animals,  and  under  existing  notions  he 
cannot  experiment  upon  men.  And  then  the  work  is 
necessarily  very  slow.  The  thought  of  the  present  time  de- 
mands absolute  demonstration.  No  possible  error  is  admis- 
sible. Dr.  Koch  spent  two  years  in  cultivating  the  bacillus 
tuberculosis  and  making  inoculations  with  it,  before  he  was 
satisfied  to  announce  it.  He  induced  the  disease  by  inocula- 
tion with  this  bacillus  in  over  one  hundred  different  animals, 
watched  most  of  them  until  death  from  the  disease  induced, 
and  examined  them  macroscopically  and  microscopically,  to 
be  absolutely  sure  there  was  no  mistake.  This  is  what  the 
scientific  world  will  demand  in  case  of  each  and  every  disease. 
The  work  will  be  very  slow,  and  years  will  be  required  for  its 
accomplishment. 

THE  EVIDENCE. 

The  evidence  that  disease-producing  bacteria  are  distinct 
from  the  bacteria  of  the  decompositions  is  now  becoming  very 
clear.  All  the  decompositions  swarm  with  bacteria  of  various 
kinds,  that  are  entirely  free  from  any  causative  relation  to 
disease,  and  evidently,  may  be  tolerated  in  food  or  in  contact 
with  the  mucous  membranes,  and  even  in  wounds,  without 
any  injury  whatever.  Every  one  who  eats  butter  which  has 
become  even  a  little  strong,  consumes  a  great  number  of 
organisms,  and  yet  without  the  least  injury.  The  same  is  true 


70  THE   GERM   THEORY   OF   DISEASE. 

of  many  other  articles  of  food.  It  also  seems  probable,  from 
many  observations,  that  the  results  of  decomposition,  as  it  pro- 
ceeds to  the  destruction  of  nitrogenous  compounds,  flesh  and 
the  like,  destroys  most  disease  germs  such  bodies  may  contain 
at  the  time  of  death. 

It  has  been  remarked  by  a  considerable  number  of  observers 
that  blood  poisoning  from  dead  bodies  will  occur  only  before 
such  bodies  have  proceeded  far  in  the  process  of  decomposi-* 
tion.  It  seems  that  inoculations  made  with  the  fluid  product 
of  nearly  complete  decompositions  do  not  produce  character- 
istic blood  poisoning.  This  is  very  distinctly  asserted  by  Dr. 
Lionel  S.  Beale,  who  regards  it  as  a  strong  argument  in  favor 
of  his  hypothesis.  He  supposes  that  the  bioplasts  whicli 
cause  disease  die  during  the  process  of  decomposition,  which, 
he  thinks,  could  not  be  claimed  in  the  case  of  bacteria.  How- 
ever, the  fact  that  one  bacterium  is  often  destroyed  in  the 
presence  of  another,  probably  by  the  waste  product  of  the 
second  being  poisonous  to  the  first,  is  now  pretty  well  estab- 
lished, and  fully  accounts  for  the  facts  observed.  Alcohol  is 
the  proper  food  of  the  mycoderma  aceti,  but  the  vinous  yeast 
plant  will  not  thrive  in  acetic  acid. 

There  is  much  reason,  now,  to  suppose  that  disease  germs  are 
less  plentiful  in  the  air  than  was  thought  a  few  years  ago.  It 
is  shown  that  a  multitude  of  germs  that  induce  decomposition 
are  not  even  capable  of  living  in  the  blood  or  tissues  of  men 
or  animals  when  placed  in  them.  The  bacterium  lactis,  which 
flourishes  in  milk  and  in  the  animal  secretions  generally,  will 
not  grow  in  the  blood  or  tissues  of  an  animal.  Also  the  bac- 
terium termo,  which  is  so  widely  spread,  and  common  in 
almost  every  atmosphere,  and  is  now  generally  considered  to 
be  the  cause  of  the  ill-smelling  putrefactions,  will  die  in  the 
living  tissues  or  blood  of  an  animal.  Great  numbers  of 
organisms  grow  in  the  mouth  of  almost  every  individual,  and 


THE   EVIDENCE.  71 

we  have  seen  them  on  the  margins  of,  and  in  wounds  of  the 
mucous  membranes,  without  in  any  wise  interfering  with  the 
healing  process. 

It  would  be  a  great  mistake,  however,  to  suppose,  from 
these  facts,  that  disease-causing  germs  are  never  present  in 
such  situations.  They  may,  at  any  time,  mingle  with  the 
harmless  varieties,  and  leaving  these,  enter  the  neighboring 
parts  or  circulation,  and  produce  their  legitimate  results, 
namely,  sickness  of  some  specific  kind. 

Disease-producing  organisms  vary  very  much  in  their 
power  of  gaining  entrance  into  healthy  blood  or  tissue.  The 
bacillus  septicus  and  the  cocco-bacterium  of  gangrene,  the 
most  virulent  organisms  known,  are  totally  unable  to  enter 
normal  structures.  They  must  enter  through  some  breach 
in  the  surface,  or  await  the  weakening  effect  of  other  disease, 
to  let  them  in  by  way  of  the  mucous  membranes.  But  once 
within  the  tissues,  the  strongest  must  yield  to  them.  Others 
of  a  less  virulent  nature  can,  of  themselves,  make  the  attack 
successfully  without  any  breach  of  tissue  or  weakening  effect 
of  other  disease.  Such  are  the  spirillum  of  relapsing  fever, 
the  organism  of  diphtheria,  and  undoubtedly,  also,  most  of 
those  of  the  contagious  diseases.  Still  others  may  gain  ad- 
mission without  a  breach  of  continuity,  but  much  more 
readily  enter  through  some  such  breach,  as,  for  instance,  the 
bacillus  of  erysipelas. 

It  will  thus  be  seen  that  a  man,  perfect  in  all  his  parts,  may 
go  among  some  of  the  more  virulent  of  these  organisms  with- 
out fear.  He  may  enter  the  dissecting  room  and  work  for 
weeks,  and  even  years,  among  the  septic  germs,  dipping  his 
hands  freely  into  the  tissues  and  fluids,  so  long  as  his  skin  is 
perfect.  But  a  slight  scratch  upon  a  finger  may  let  in  the 
septic  germs  that  will  speedily  cause  his  death. 


72  THE   GERM   THEORY   OF   DISEASE. 

SPORES— HABITS. 

It  seems  well  demonstrated  that  a  number  of  the  lower 
forms  of  life,  bacteria,  mycoderma,  saccharomyces,  etc.,  form 
their  spores  under  conditions  other  than  those  best  suited  to 
the  active  growth  of  the  plant.  From  a  close  scrutiny  of  the 
manner  and  time  of  spore  formation  of  these  life  forms,  it 
seems  that  they  are  formed  only  under  conditions  which 
slowly  destroy  the  activity  of  the  plant.  The  yeast  plant 
forms  spores  only  after  fermentation  has  ceased  and  its  multi- 
plication by  budding  hindered.  It  has  been  asserted  that  the 
bacillus  anthracis  will  form  spores  in  the  cultivation  flasks 
only  when  the  temperature  has  been  allowed  to  fall  below 
that  of  the  blood,  and,  therefore,  cannot  form  them  until 
eliminated  from  the  animal  in  which  they  grow,  or  after  the 
death  of  the  animal. 

A  considerable  number  of  organisms,  whose  natural  habitat 
seems  to  be  fruits,  such  as  grapes,  cherries,  etc.,  form  spores 
only  when  drying  occurs ;  that  is,  the  plant  lives  on  the  fruit, 
multiplying  by  budding  or  by  fission  ;  but  when  the  fruit 
gives  out  and  drying  up  begins,  the  formation  of  spores  begins 
also.  This  seems  to  be  the  controlling  factor  in  spore  forma- 
tion in  a  large  number  of  the  bacterial  forms.  And  the 
philosophy  of  this  act,  when  we  consider  it,  is  rather  beau- 
tiful, and  would  seem  to  be  a  special  fitness  of  function  to 
needs.  Rapid  multiplication  by  the  simple  plan  occurs  in  the 
presence  of  suitable  conditions  for  activity.  When  these  con- 
ditions begin  to  fail  comes  the  organization  of  the  spores 
destined  to  preserve  vitality  under  conditions  unfit  for  active 
growth. 

The  facts  now  at  our  disposal  will  not  warrant  the  conclu- 
sion that  this  is  a  law  of  spore  formation  for  all  these  organ- 
isms. Indeed,  we  have  facts  which  directly  controvert  this 
proposition. 


SPORES — HABITS.  73 

If  Dr.  Koch  has  traced  the  life  history  of  the  bacillus 
tuberculosis  aright,  it  multiplies  only  by  the  formation  of 
spores,  never  by  fission  or  budding,  and  the  spores  are  formed 
under  the  conditions  of  the  activity  of  the  organism.  Only 
this  one  instance  of  this  exclusive  multiplication  by  spores  is 
recorded,  however,  in  the  whole  field  of  research  among  these 
forms  of  life.  Many,  however,  have  been  found  to  form 
their  spores  during  the  continuance  of  the  conditions  of  their 
activity,  as  the  bacillus  septicus,  micrococci  of  gangrene,  and 
some  others. 

These  facts  have  a  very  important  bearing  upon  the  modes 
of  communication  of  contagious  and  infectious  diseases,  and 
may  finally  serve  to  explain  some  of  their  peculiarities.  For 
instance,  if  it  is  found  that  a  disease-producing  organism  pro- 
duces spores  only  when  there  is  a  lack  of  moisture,  or  at  a 
temperature  below  that  of  the  human  blood,  it  will  be  clear 
that  the  spores  will  be  produced  only  after  elimination  of  the 
organisms.  If,  in  connection  with  this  fact,  it  is  found  that 
the  developed  organism  is  destroyed  by  drying,  which  is 
inferred,  then  it  becomes  clear  that  infection  will  not  be  likely 
to  take  place,  through  the  medium  of  the  air,  directly  from 
the  sick  to  the  well.  Drying  of  the  eliminated  organisms 
must  first  occur,  during  which  the  spores  are  formed,  'and  then 
the  drying  must  be  continued  until  the  particles  are  ready  to 
be  wafted  about  by  the  air  currents  and  in  this  manner  be 
carried  to  the  well  persons.  Dr.  E.  D.  Salmon  (Medical 
Record  for  April,  1883)  has  developed  the  idea  that  the  intro- 
duction of  the  spores  of  the  bacillus  anthracis  produces  a 
different  result  from  the  inoculation  with  the  developed  organ- 
ism, under  certain  conditions. 

If  this  bacillus  be  cultivated  continuously  under  conditions 
which  will  not  allow  of  spore  formation,  it  will  be  weakened 
in  virulence,  so  that  its  introduction  will  cause  a  mild  type  of 


74  THE   GERM   THEORY   OF   DISEASE. 

the  disease.  If,  however,  this  weakened  bacillus  be  allowed 
to  form  spores,  these  spores  will  produce  the  virulent  type  of 
the  disease.  If  this  observation  be  confirmed  by  further  re- 
search, it  will  become  an  important  element  in  sanitary  and 
prophylactic  measures,  especially  so  if  it  be  found  true  of  any 
considerable  number  of  disease  germs. 

It  will  be  seen  at  once  that  the  thought  contained  here  has 
an  important  bearing  upon  the  propagation  of  yellow  fever, 
cholera  and  typhoid  fever.  If  we  suppose  that  the  power  of 
forming  spores  only  comes  with  more  or  less  gradual  drying 
of  the  voided  organisms,  and  that  these  organisms  are  not 
eliminated  by  the  lungs  and  sweat  glands  but  only  with  the 
excreta,  therefore,  not  liable  to  be  transplanted  by  immediate 
passage  through  the  air,  we  are  at  once  able  to  understand 
the  clinical  facts  observed  as  to  communicability  of  these 
diseases. 

SUMMING  UP. 

Having  passed  in  review,  briefly,  the  rise  and  progress  of 
the  Germ  Theory  of  Disease,  we  may  sum  up  the  principal 
points  thus : — 

1st.  In  the  seventeenth  and  eighteenth  centuries,  intelligent 
observers  of  contagious  diseases,  after  much  study  of  the  sub- 
ject, came  to  the  conclusion  they  were  caused  and  propagated 
by  a  process  identical  with  or  similar  to  fermentation  and 
decomposition. 

2d.  There  was  much  study  of  the  processes  of  fermentation 
and  decomposition,  in  order  to  arrive  at  a  more  clear  under- 
standing of  the  causes  of  epidemic  and  contagious  diseases 
with  the  view  of  prevention  and  cure.  These  experiments 
demonstrated  that  the  fermentations  and  decompositions  were 
something  different  from  ordinary  chemical  phenomena. 

3d.  The  yeast  plant  was  discovered  by  Schwan  and  Latour, 
in  1838.  These  gentlemen  announced  distinctly  that  the 


SUMMING    UP.  75 

chemical  changes  of  vinous  fermentation  are  caused  by  the 
life  and  growth  of  this  plant.  They  disproved,  by  experiment, 
the  previous  hypothesis,  that  oxygen  is  the  active  agent  in  any 
of  the  similar  processes ;  and,  reasoning  from  this  discovery, 
came  to  the  conclusion  that  all  the  fermentations,  decompo- 
sitions, miasms  and  contagions  were  caused  by  the  life  force. 

4th.  These  conclusions  were  attacked  by  chemists,  notably, 
by  Professor  Liebig,  who  denied  both  the  facts  claimed  and 
the  conclusions  arrived  at,  since  which  time  there  has  been  a 
continuous  discussion  of  the  subject. 

5th.  In  1854,  Schroeder  conclusively  disproved  the  exist- 
ence of  gaseous  ferments  claimed  by  chemists,  by  admitting 
air  filtered  through  cotton  batting  to  sterilized  fluids  without 
causing  fermentation. 

6th.  From  1857  to  1861  Pasteur  successfully  worked  out 
all  the  more  ordinary  fermentations  by  his  fractional  flask 
cultivations,  and  proved  each  of  them  to  have  a  specific  plant 
growth  as  its  cause.  He  also  showed  that  none  of  the  decom- 
positions  could  proceed  without  living  organisms,  though  the 
specific  organism  belonging  to  each  was  not  clearly  made  out. 

7th.  Basing  his  efforts  on  the  results  of  the  last  two,  Mr. 
Lister  introduced  his  antiseptic  treatment  of  wounds,  in  1865, 
which  has  proved  a  panacea  for  most  of  the  dreaded  in- 
fectious wound  troubles  in  all  hospital  surgical  practice. 

8th.  M.  Pasteur,  Dr.  Koch  and  others  have  succeeded  in 
isolating  a  number  of  distinct  disease-producing  germs,  and 
causing  the  specific  diseases  in  animals,  regularly,  by  planting 
these  germs  under  the  skin,  and  Dr.  Koch,  especially,  has 
succeeded  in  doing  this  after  freeing  the  organisms  of  all 
possible  following  of  decomposing  matter  by  growing  them 
upon  dry  slides. 

9th.  This  much  having  been  proven,  the  continued  obser- 
vation of  numerous  other  organisms  of  distinct  form  and 


76  THE   GERM    THEORY   OF   DISEASE. 

character,  always  associated  with  specific  forms  of  disease, 
warrants  the  inference  that  these  diseases  are  also  caused  by 
specific  organisms. 

10th.  All  the  foregoing  taken  together  gives  strong  pre- 
sumptive evidence  that  all  contagious  and  infectious  diseases 
are  produced  by  disease  germs. 


PART    SECOND. 


FOURTH  LECTURE. 

THE  RELATION  OF  MICRO-ORGANISMS  TO  THE 
PRODUCTION  OF  DISEASE. 

One  who  has  followed  closely  the  experimentation  on  the 
relation  of  micro-organisms  to  the  production  of  disease,  will, 
I  think,  accept  the  following  propositions  as  a  basis  for  a 
farther  study  of  the  subject: — 

1st.  Experiment  has  shown  that  there  are  many  micro- 
organisms which  do  not  produce  disease  or  injury;  that  the 
mere  presence  of  these  life  forms  is  not,  in  itself,  a  sufficient 
cause  of  disease;  but  that  there  are  certain  micro-organisms 
that  uniformly  induce  disease  when  they  are  planted  in,  or 
obtain  entrance  to,  the  bodies  of  animals  or  men. 

2d.  All  through  the  experimentation  that  has  been  had  on 
this  subject,  it  has  been  noticed  that  poisons  have  originated 
in  connection  with  the  disease-producing  organisms. 

3d.  These  poisons  seem  to  be  a  product  of  the  organisms, 
and,  while  produced  only  in  connection  with  the  life  and 
growth  of  the  microscopic  plants,  may  be  separated  from 
them ;  and,  when  so  separated,  produce  direct  poisoning 
similar  to  that  induced  by  the  poisons  from  the  higher  plants. 

4th.  This  poisoning  is  different  from  the  disease  that  is 
induced  by  the  organisms,  in  that  it  is  direct,  and  compara- 
tively immediate;  while  infectious  disease  arises  only  after  a 
more  or  less  definite  stage  of  incubation. 

5th.  Therefore,  it  is  probable  that  each  infectious  disease  is 
caused  by  a  micro-organism  that  is  capable  of  developing  in 
the  tissues,  or  blood,  and  forming  poisons  through  changes 
wrought  in  the  molecular  forms  of  matter,  by  virtue  of  its 

79 


80  THE   GERM   THEORY   OF   DISEASE. 

vital  energies;  or,  the  physiological  processes  of  digestion, 
nutrition  and  the  formation  of  waste  products. 

These  considerations  suggest  an  extended  examination  of 
the  physiological  phenomena  of  life,  in  its  varied  forms,  as 
related  to  matter,  as  the  best  means  of  gaining  a  clear  concep- 
tion of  the  teachings  of  the  facts  developed  by  experiment. 
It  will  be  seen  by  any  one  who  reviews  this  whole  subject 
closely  that,  while  the  experimentation  that  has  been  had  fur- 
nishes the  strongest  evidence  that  disease  results  from  the 
presence  of  micro-organisms  (is  brought  about  in  some  way 
through  the  life  and  growth  of  these  lowly  forms),  the  modus 
operandi  by  which  they  induce  disease  has  not  been  explained, 
or  such  explanation  has  been  but  partial. 

Indeed,  thus  far,  the  principal  effort  has  been  to  show  that 
micro-organisms  are  regularly  connected  with  certain  pro- 
cesses of  disease,  and  that  these  in  no  case  occur  without  this 
accompaniment,  rather  than  to  show  how  they  induce  disease. 
This  was  necessary,  in  the  beginning  of  this  work,  for  the 
collection  and  collation  of  sufficient  data  upon  which  to  con- 
struct theories,  and  found  a  basis  of  truth,  from  which  inquiry 
might  proceed  to  the  more  perfect  unfolding  of  the  mysteries  of 
this  important  subject.  The  Germ  Theory  of  Disease,  as  it 
stands  to-day,  is  essentially  a  mass  of  unexplained  facts,  devel- 
oped by  direct  experiment  of  the  most  subtle  nature;  so  subtle, 
indeed,  that  there  are  but  few  men  who  have  the  natural  endow- 
ments and  rigid  training  necessary  to  verify  them  in  a  manner, 
and  with  the  certainty,  that  the  thought  of  the  times  demands. 

Under  these  circumstances,  and  with  the  plain  fact  before 
us  that  the  mere  presence  of  the  organisms  is  not  a  sufficient 
cause  of  the  diseases  that  experiment  teaches  us  are  induced  by 
them,  we  naturally  turn  to  the  well  demonstrated  fact  that 
micro-organisms  do  give  rise  to  poisons,  for  an  explanation  of 
these  phenomena.  It  is  our  purpose  now  to  make  an  effort 


PROPOSITIONS.  81 

to  trace  certain  of  the  phenomena  presented  by  the  life  force 
in  its  relations  to  matter,  with  the  end  in  view  of  elucidating 
this  difficult  point.  In  this  direction,  as  it  seems  to  me,  we 
are  most  likely  to  find  a  satisfactory  explanation  for  some  of 
the  teachings  of  experiment  that  have  seemed  difficult  to 
understand.  In  these  brief  lectures,  however,  we  can  only 
glance  at  the  principal  points  necessarily  involved  in  a  com- 
plete discussion  of  the  subject. 

The  phenomena  that  we  will  now  review  will  be  Digestion, 
Absorption,  Nutrition,  and  the  Formation  of  Waste  Products 
in  the  several  forms  of  life ;  after  which  we  will  study  briefly 
the  relation  which  the  changed  forms  of  matter,  produced  by 
the  physiological  activity  of  micro-organisms,  may  hold  to 
the  production  of  disease.  This  is  necessarily  a  biological 
study. 

DIGESTION. 

Digestion  is  a  process  of  solution  and  chemical  reorganiza- 
tion of  food  material,  by  which  it  is  fitted  for  reception  by  the 
life  force,  or  is  brought  within  the  sphere  of  chemico-vital 
influences.  The  material,  when  thus  prepared,  is  conveyed 
within  the  organism  by  absorption  or  osmosis.  Digestion 
and  absorption  are  the  admitted  forerunners  of  all  nutritive 
processes — the  initial  steps  by  which  nutrition  is  rendered 
possible.  This  is  true  of  all  the  varied  forms  in  which  the 
life  force  is  manifest,  from  the  most  minute  micrococcus  to 
man.  There  are  substances  made  use  of  by  the  life  force 
without  digestion  previous  to  absorption,  but  every  living 
thing  is  provided  with  this  mode  of  food  preparation. 

PROPOSITIONS. 

1st.  All  digestion  is  accomplished  by  soluble  ferments, 
elaborated  by  the  organism,  whether  this  digestion  be  accom- 
plished in  a  stomach,  alimentary  canal,  or  elsewhere. 


82  THE   GERM   THEORY   OF   DISEASE. 

2d.  Digestion  is  threefold  in  its  forms :  (a)  Primary,  (b) 
Absorptive  or  Resorptive.  (c)  Nutritive  or  Assimilative. 

Primary  digestion  is  the  ordinary  method  by  which  food  is 
fitted  for  reception  by  the  organism.  It  is  accomplished  by 
a  soluble  ferment,  or  ferments,  secreted  by  the  organism  and 
thrown  out  (a)  into  a  cavity,  stomach  or  intestinal  canal,  into 
which  the  digestible  material  is  brought;  (6)  into  the  sur- 
rounding media  in  which  digestible  material  is  suspended,  or 
upon  digestible  solids  or  semi-solids. 

Absorptive  and  resorptive  digestion  is  accomplished  among 
the  ordinary  tissues,  by  a  soluble  ferment  elaborated  by  the 
tissues,  under  special  circumstances:  (a)  For  the  removal  of 
tissues  no  longer  needed,  as  roots  of  temporary  teeth,  of  bone 
during  changes  of  form,  and  of  other  tissues  after  their  purpose 
has  been  served — resorptive  digestion.  (6)  For  the  removal 
of  substances  accidentally  lodged  in  the  tissues,  as  animal 
membrane  and  catgut  ligatures,  etc. — absorptive  digestion. 

Nutritive  digestion  is  performed  within  the  tissues  them- 
selves, and  by  them.  It  is  the  act  of  assimilation,  the  act  by 
which  nutritive  material  is  converted  into  tissue  and  formed 
material. 

Primary  digestion,  in  the  higher  animals,  is  performed  in 
the  alimentary  canal.  This  is  accomplished  by  the  aid  of 
certain  substances  known  as  soluble  ferments.  The  term 
soluble  ferment  is  used  to  denote  a  very  different  thing  from 
an  organic  ferment.  An  organic  ferment  is  always  com- 
posed of  living  cells,  and  is  therefore  insoluble.  A  soluble 
ferment  performs  the  act  of  digestion  only,  and  is  not  capable 
of  reproduction ;  while  an  organic  ferment  performs  all  the 
acts  of  complete  fermentation,  and  is  capable  of  continuous 
reproduction.  All  soluble  ferments  are  products  of  the 
activity  of  cell  life,  or  of  the  life  force  in  the  cell  form.  In 
the  stomach  it  is  found  that  certain  cells,  forming  the  peptic 


PROPOSITIONS.  83 

glands,  secrete  a  fluid  rich  in  pepsin,  which  constitutes  the 
true  soluble  ferment  of  the  stomach,  the  office  of  which  is  the 
conversion  of  food  of  certain  known  qualities  into  peptones  or 
chyme.  The  pancreas  elaborates  another  soluble  ferment, 
pancreatin,  or  trypsin,  which  acts  upon  another  portion  of 
the  food.  Other  portions  of  the  alimentary  tract  furnish 
other  soluble  ferments,  which  in  their  turn  act  upon  the  food. 
The  combined  effect  of  all  these  is  to  fit  the  food  for  reception 
by  the  blood,  through  the  process  known  as  osmosis. 

It  will  be  seen  at  once  that  these  processes  of  digestion  are, 
in  fact,  extraneous  to  the  body ;  that  is,  they  are  in  receptacles 
in  which  food  material  is  met  by  appropriate  soluble  ferments, 
by  which  it  is  dissolved  and  its  chemical  constituents  re-ar- 
ranged, remoleculized.  (I  use  the  word  "remoleculize"  to 
designate  that  disturbance  or  change  of  the  molecular  form 
of  matter  which  occurs  under  the  influence  of  the  life  force. 
As  an  example,  I  may  take  the  change  that  occurs  in  starch 
in  the  presence  of  saliva,  which  is  expressed  in  the  following 
formula : — 

Starch.  Water.  Glucose. 

C6H1005  +  H20  =  C6H1206 

It  will  be  seen  here  that  the  digestive  body,  ptyaline,  does 
not  enter  into  combination,  but,  by  its  presence,  causes  a  com- 
bination of  the  water  and  starch,  producing  a  remoleculization 
with  the  formation  of  glucose.  Again,  the  digestive  body 
given  out  by  the  yeast  plant,  when  in  contact  with  cane  sugar, 
dissolved  in  water,  induces  the  following  changes : — 

Cane  Sugar.  Water.  Glucose.  Lavelose. 

C^H^On  +  H20  ==  C6H1206  +  C6H1206 
This  result  is  different  in  that  two  new  bodies  are  formed 
by  the  juncture  of  the  two  with  which  we  began.     In  the  use 
of  the  word  we  apply  it  to  any  possible  molecular  change, 
without  expressing  the  character  of  that  change.     We  may 
say  that  the  yeast  plant  destroys  sugar  by  remoleculizing  it, 
5 


84  THE   GERM   THEORY   OF   DISEASE. 

or  that  alcohol  is  a  product  of  the  remoleculization  of  sugar 
by  the  vinous  yeast  plant,  etc.) 

It  is  also  sufficiently  established  that  these  soluble  ferments 
will  act  upon  food  material  just  as  well  when  removed  from 
the  cavities  of  the  body  as  in  them,  provided  a  proper  tem- 
perature be  maintained.  This  fact  shows  that  soluble  fer- 
ments, while  formed  only  by  the  life  force,  when  once  formed, 
act  without  the  life  force.  A  soluble  ferment  is  not  itself 
alive. 

FERMENTS. 

An  example  of  digestion  without  a  stomach,  or  the  act 
of  digestion  of  food  material  suspended  in  a  surrounding 
medium,  is  found  in  vinous  fermentation;  which  is  accom- 
plished by  the  torula,  saccharomyces  cerevisia,  or  yeast  plant. 

The  history  of  the  plant  is  too  well  known  to  need  descrip- 
tion or  affirmation,  other  than  the  points  needed  for  illustration. 
When  pure  vinous  yeast  is  washed  with  distilled  water,  a 
peculiar  substance  is  found  dissolved  in  the  water.  This  is 
yielded  continuously  during  the  life  of  the  plant.  Examina- 
tion has  proven  this  substance  to  be  a  soluble  ferment,  having 
a  peculiar  effect  upon  sugar.  This  has  been  examined  by  M. 
Berthelot,  M.  Becamp  and  others.  It  has  been  precipitated 
and  obtained  in  the  form  of  a  powder,  somewhat  similar  to 
Pepsin,  and  when  redissolved,  has  been  found  to  retain  its 
original  action  upon  cane  sugar.  This  action  is  to  split  up 
the  sugar  into  two  substances,  called  Glucose  and  Lavelose, 
the  formulae  of  which  we  have  given  above. 

This  reaction  always  takes  place  as  the  primary  step  in 
alcoholic  fermentation,  and  is  the  primary  digestion  which 
permits  of  the  appropriation  of  the  food  material  by  the  yeast 
plant.  This  is  entirely  analogous  to  the  digestion  of  food  in 
the  stomach  of  an  animal,  by  which  such  food  is  received  by 
the  blood  to  be  conveyed  to  the  tissues  for  their  nutrition  ; 


FERMENTS.  85 

but  it  is  accomplished  in  the  surrounding  media  instead  of  in 
a  receptacle  provided  for  the  purpose,  an  alimentary  canal. 
This  is  one  instance  of  a  type  of  digestion  which  I  believe  to 
be  universal  in  case  of  all  unicellular  animals  and  plants. 
The  formation  of  a  stomach  is  a  provision  for  the  conserva- 
tion of  force,  but  it  in  no  way  changes  the  modus  operandi 
of  the  digestive  function. 

Now,  if  I  have  been  understood  thus  far,  you  will  probably 
be  enabled  to  understand  the  import  of  certain  experiments 
which  have  seemed  involved  in  mystery.  I  will  again  refer 
to  a  series  of  experiments  by  Mr.  Lister,  mentioned  in  my 
last  lecture,  in  which  he  says  that  he  tried  a  large  number  of 
experiments  in  which  he  found  unmistakably  that  "it  re- 
quired several  drops  of  tap-water  (London  hydrant  water),  in 
which  there  were  bacteria  termo,  usually  one,  to  two,  or 
three,  in  a  drop,  to  start  putrefaction  in  blood  serum ;  while 
the  least  possible  portion  of  putrefying  blood  (containing, 
probably,  no  greater  number  of  bacteria),  would  start  it  at 
once."  He  wondered  at  this,  and  says  that  "it  may  be  that 
some  substance  adheres  to  the  bacteria,  or  is  present  in  the 
portion  of  decomposing  blood,  that  starts  the  decomposition ; 
whereas,  the  bacteria  washed  with  pure  water  are  free  from 
this." 

In  another  paragraph,  Mr.  Lister,  always  close  to  the  front 
when  searching  for  truth,  strikes  much  nearer  the  mark.  He 
says  :  "  Or  again,  it  seems  to  me  conceivable  that  the  normal 
serum  may  oppose  an  insuperable  obstacle  to  the  nutritive  at- 
tractions of  an  individual  bacterium,  but  that  this  may  be 
overcome  by  the  associated  action  of  several  of  the  organisms 
in  close  proximity,  after  the  analogy  of  the  more  energetic 
operation  of  a  concentrated  solution  of  a  chemical  reagent. 
But  whatever  be  the  explanation,  the  fact  remains."  In  this 
paragraph  we  find  a  close  statement  of  what  seems  to  me  to 


86  THE   GERM   THEORY   OF   DISEASE. 

be  the  physiological  fact  in  the  case,  only  Mr.  Lister  seems 
not  to  have  reached  the  point  of  recognizing  the  general  phy- 
siological law  appertaining  to  this  subject. 

I  should  explain  the  phenomena  in  this  wise ;  the  soluble 
ferment,  diastase,  or  digestive  agent  given  out  by  this  bacteri- 
um, must  attain  to  a  certain  degree  of  intensity,  or  concentra- 
tion, before  it  is  capable  of  acting  on  blood  serum.  A  single 
bacterium  is  incapable  of  forming  a  sufficient  quantity  of 
soluble  ferment,  when  dissipated  among  the  serum,  to  accom- 
plish this  digestion,  and  being  incapable  of  appropriating  the 
undigested  material,  dies  of  dyspepsia;  while,  if  a  large  num- 
ber are  massed  together,  there  is  a  corresponding  concentration 
of  the  ferment  substance,  the  digestion  of  the  serum  is  accom- 
plished, and  the  colony  will  flourish.  The  serum  is  speedily 
decomposed. 

The  soluble  ferment  of  B.  termo  has  been  practically 
demonstrated  by  Wortnian,  who  has  shown  that  starch  may 
be  remoleculized  by  this  organism  if  no  other  source  of  car- 
bon is  available.  And  that  in  this  case  a  diastase  (soluble 
ferment)  is  secreted  which  first  transforms  the  starch  into 
sugar  (glucose),  which  is  consumed  by  the  bacteria  as  fast  as 
formed.  If  a  potato  be  boiled  and  a  slice  cut  from  it  smoothly, 
to  expose  the  surface,  and  this  surface  be  exposed  to  the  air 
for  a  few  minutes,  in  order  that  a  few  germs  that  may  be 
floating  in  the  air  may  light  upon  it,  and  this  be  protected 
afterwards  from  other  germs  by  a  bell-glass  covering,  with 
sufficient  water  to  prevent  drying,  there  will  be  a  develop- 
ment of  clusters  of  bacteria  lying  upon  the  surface.  In  or- 
dinary summer  temperature  this  may  be  seen,  usually,  after 
two  or  three  days,  as  small  points  of  varying  colors.  Now, 
if  these  points  be  removed,  one  by  one,  and  examined  with 
the  aid  of  a  microscope,  it  will  be  found  that  each  little  cluster 
is,  as  a  rule,  made  up  of  micro-organisms  of  one  distinct 


FERMENTS.  87 

variety,  but  the  different  clusters  will  usually  be  of  different 
varieties.  Each  of  these  has  evidently  developed  from  a 
single  germ  or  spore  which  has  happened  to  fall  at  that  spot. 
By  what  means  do  these  bacteria  appropriate  the  starch  of  the 
potato  to  their  nutrition  ?  This  material  is  not,  as  we  know, 
in  a  state  fitted  for  the  nutrition  of  these  organisms;  nor, 
even  in  a  condition  in  which  it  can  be  taken  up  by  osmotic 
action.  The  starch  must  be  digested  before  it  can  be  appro- 
priated. That  this  digestion  really  takes  place  may  easily 
be  shown.  If  we  prepare  the  potato  as  above  described, 
watch  it  until  the  micro-organisms  have  grown  to  a  greater 
extent — until  they  have  spread  over  the  surface  and  the 
little  clusters  have  coalesced  with  each  other — then  cut  a 
very  thin  slice  from  the  surface,  and  submit  this  to  the  chem- 
ical test,  we  will  find  that  a  part  of  the  starch  has  been 
changed  into  glucose,  or  some  form  of  sugar.  This  change 
is  the  usual  first  act  in  digestion  by  plants,  when  starch  is 
the  substance  acted  upon,  and  is  the  primary  digestion  per- 
formed by  the  diastase,  or  soluble  ferment  secreted  by  these 
organisms  for  the  preparation  of  their  food.  This  change 
goes  on  very  rapidly,  and  the  greater  part  of  the  sugar  formed 
is  at  once  appropriated  to  the  nutrition  of  the  organisms,  and 
its  molecular  form  again  changed.  In  the  earlier  stages  of 
the  process  or  growth,  it  is  probable  that  the  sugar  formed  is 
very  nearly  all  used  as  fast  as  formed,  but  when  the  growth 
becomes  very  luxuriant,  there  is  a  superabundant  digestion 
which  permits  us  to  find  the  traces  of  the  sugar,  which  reveals 
the  manner  in  which  the  nutrition  of  the  little  plants  is 
brought  about. 

This  process  will  continue  until  every  particle  of  the  starch 
has  been  remoleculized.  But  this  is  only  one  of  the  series  of 
remoleculizations  which  take  place.  The  starch  is  converted 
into  sugar,  the  sugar  into  tissue  of  the  growing  plants,  and 


88  THE   GERM   THEORY   OF   DISEASE. 

during  all  this  process  the  plants  are  giving  off  waste  products. 
These  waste  products  mingle  with  the  remains  of  the  potato, 
giving  to  it  its  offensive  qualities,  and  it  is  said  to  be  rotting. 
We  learn  from  this  study  that  it  is  not  necessary  that  food 
material  be  dissolved  in  liquid  in  order  that  it  may  be  ap- 
propriated by  bacteria.  They  are  able  to  furnish  a  solvent 
which  will  bring  it  into  a  condition  fitting  it  for  osmosis. 
Otherwise  bacteria  would  be  utterly  incapable  of  attacking 
solids  or  semi-solids.  Yet  the  cultivation  of  the  pathogenic 
micro-organisms  on  solidified  media  has  been  rendered  popu- 
lar by  Dr.  Koch,  of  Berlin,  and  it  is  now  fully  established 
that  they  grow  well  upon  such  food.  This  was  described  in 
my  last  lecture,  and  is  very  similar  to  the  growing  of  the 
organisms  on  the  potato  just  described,  and  illustrates  the 
same  physiological  laws.  Indeed,  it  seems  to  have  been  the 
observation  of  the  growth  on  the  potato  that  led  Dr.  Koch 
to  the  dry  slide  method.  By  this  method,  solid  food  mate- 
rials may  be  prepared  that  are  suited  to  the  wants  of  the  par- 
ticular organism ;  and,  so  far  as  I  am  informed,  any  of  the 
micro-organisms  may  be  successfully  cultivated  by  this  plan, 
if  sufficient  skill  is  used  in  the  selection  and  preparation  of 
the  material.  Under  these  conditions  it  could  not,  reasonably, 
be  expected  that  the  food  material  could  be  imbibed  by  the 
organisms  unless  they  could  furnish  some  solvent  by  which 
it  is  brought  into  a  condition  fitting  it  for  osmotic  action. 

All  these  facts  point  unmistakably  to  the  formation  of 
soluble  ferments  by  the  organisms,  which  serve  the  purpose, 
not  only  of  liquefying,  but  of  changing  the  molecular  form  of 
food  material ;  a  process  in  which  the  analogy  to  digestion,  or 
conversion  of  food  material  into  peptones  in  the  stomachs  of 
the  higher  animals,  is  perfect. 

Many  of  the  micro-organisms  seem  specially  adapted  to 
certain  foods,  and  their  digestive  solvents  are  such  as  to  serve 


PLANTS.  89 

the  special  purpose,  as  is  seen  in  the  amraouiacal  fermentation 
of  urine.  "  M.  Musculus  has  shown  that  we  may  obtain  from 
altered  urine  a  soluble  ferment.  Upon  adding  to  it  highly-con- 
centrated alcohol  a  precipitate  is  formed  which  may  be  filtered 
and  dried.  This  precipitate,  not  at  all  organized,  transforms 
urea  into  carbonate  of  ammonia.  A  temperature  of  80°  (176° 
Fah.),  destroys  it.  This  diastase  appears,  then,  to  be  a  secretion 
of  the  micrococcus  urea,  and  perhaps  the  role  of  the  bacteria  is 
limited,  in  the  phenomena  of  fermentation,  to  the  formation  of 
this  secretion  alone.  The  ammoniacal  transformation  of  urine 
would,  consequently,  enter  into  the  group  of  fermentations  by 
the  varieties  of  diastase."  (Magnin  on  Bacteria,  page  142.) 

The  proof  here  given  of  the  production  of  a  true  digestive 
body,  or  diastase,  by  the  micrococcus  urea  is  sufficiently  positive; 
but  M.  Musculus  must  be  wrong  in  his  supposition  that  the 
"  role  of  the  micrococcus  is  limited  to  this  one  function ; "  for,  if 
the  organism  does  not  appropriate  from  the  results  of  its  diges- 
tion, wherewithal  does  it  live.  It  may  be  that  we  have  here  an 
example  of  superabundant  digestion,  which,  as  a  matter  of  fact, 
is  to  be  expected  when  the  natural  condition  is  the  diffusion  of 
the  digestive  solvent  through  masses  of  fluid  material.  But  the 
organism  must  live  by  remoleculizations  within  itself,  and  elim- 
inate waste  products.  Therefore,  the  explanation  is  incomplete. 

It  has  also  been  shown  that  the  first  changes  which  albumen 
undergoes  in  decomposition  are  similar  to  digestion.  It  is  first 
converted  into  soluble  forms,  partly  peptones,  and  afterward 
converted  into  other  forms. 

PLANTS. 

When  we  turn  our  attention  to  the  higher  forms  of  plant 
life,  we  are  beset  with  many  difficulties.  The  botanists,  it 
seems,  have,  as  a  rule,  endeavored  to  explain  the  growth  of 
plants  from  the  chemical  standpoint,  and  have  almost  univer- 


90  THE   GERM    THEORY   OF   DISEASE. 

sally  started  with  the  thought  that  the  roots  of  the  plant 
absorbed  water,  with  whatever  might  happen  to  be  dissolved 
in  it,  and  from  this  the  plant  appropriated  that  which  it  could 
use  in  the  building  of  its  tissues.  This  mode  of  reasoning 
has,  however,  failed  to  give  satisfaction.  Many  facts  have 
appeared  from  time  to  time  which  could  not  be  explained 
upon  this  supposition.  Prominent  among  these  is  the  fact 
that  material  is  continually  found  in  plants  which  cannot  be 
found  in  a  soluble  state  in  the  ground  in  which  the  plants 
grow.  Sachs  (Text-Book  of  Botany,  p.  625),  in  discussing  this 
point,  says:  "But  a  large  portion  of  food  material,  especially 
compounds  of  ammonia,  potassium  and  phosphoric  acid,  occur 
in  the  ground  in  a  fixed  conditioner  as  it  is  generally  termed, 
absorbed  ;  they  are  not  extracted  from  the  soil  by  very  large 
quantities  of  water;  the  roots,  nevertheless,  take  them  up  with 
ease.  It  may  be  supposed,  in  these  cases,  that  the  absorbed 
food  materials  occur  as  an  extremely  fine  coating  over  the 
particles  of  soil,  and  can  therefore  only  be  taken  up  together 
with  them  by  the  root  hairs  at  the  points  of  contact;  and  they 
are  there  rendered  soluble  by  the  carbon  dioxide  exhaled  by 
the  roots.  This  action  of  the  roots  is  limited  to  the  points  of 
contact;  only  those  absorbed  particles  of  substance  which  come 
directly  into  contact  with  the  root  hairs  are  dissolved  and 
sucked  up.  But,  since  the  numbers  and  length  of  the  roots  is 
very  considerable  in  all  growing  land  plants,  and  since,  also, 
they  are  continually  lengthening  and  forming  new  root  hairs, 
the  root  system  comes  gradually  in  contact  with  innumerable 
particles  of  earth,  and  can  thus  take  up  the  necessary  quantity 
of  the  substance  in  question.  This  power  of  the  roots  of  tak- 
ing up,  by  means  of  the  acid  sap,  which  permeates  the  walls 
of  even  their  superficial  cells,  substances  which  are  insoluble 
in  pure  water,  presents  itself  in  an  extremely  evident  manner, 
as  I  was  the  first  to  show. 


SPROUTING   OF   SEEDS.  91 

"When  polished  plates  of  marble,  dolomite,  or  osteolite 
(calcium  phosphate),  are  covered  with  sand,  to  a  depth  of  a 
few  inches,  and  seeds  are  then  sown  in  the  sand,  the  roots, 
which  strike  downward,  soon  meet  the  polished  surface  of 
the  mineral,  and  grow  upon  and  in  close  contact  with  it. 
After  a  few  days  an  impression  of  the  root  system  is  found 
corroded  in  rough  lines  into  the  smooth  surface ;  every  root 
has  dissolved,  at  the  points  of  contact,  a  small  portion  of  the 
mineral,  by  means  of  the  acid  water  which  permeates  its  outer 
cell  walls.'7 

Here  we  have,  clearly  set  forth,  and  proven  by  experiment, 
a  virtual  gastric  juice,  a  substance  elaborated  and  sent  out  to 
meet  food  material,  dissolve  it,  and  render  it  fit  to  be  brought 
in,  by  osmosis,  the  same  as  in  the  higher  animals  and  in  the 
lower  forms  of  unicellular  life. 

It  is  not  yet  shown,  in  this  case,  that  this  is  a  specialized 
soluble  ferment  substance,  but  it  evidently  acts  the  part  of 
such  a  substance,  and,  while  this  is  so  clearly  shown,  its  com- 
position makes  but  little  difference,  so  far  as  our  present  pur- 
pose is  concerned,  which  is  to  show  that  all  forms  of  life  are 
dependent  upon  digestion  in  some  form,  for  the  preparation 
of  the  material  upon  which  they  subsist  for  absorption. 

It  is  not  claimed  that  all  material  used  by  the  life  force 
must  undergo  this  kind  of  change.  Water  is  used  without 
such  change  by  all  forms  of  life,  and  probably  many  other 
substances  are  so  used. 

SPROUTING  OF  SEEDS. 

With  every  egg  that  is  formed  there  is  a  provision  for  the 
nourishment  of  the  embryo  until  the  animal  has  developed 
the  organs  by  which  it  is  to  prepare  its  food  for  assimilation. 
The  egg  is  composed  of  two  parts,  an  embryo,  and  formed 
material  for  the  nutrition  of  that  embryo.  In  the  seed  there 
5* 


92  THE   GERM   THEORY   OF   DISEASE. 

is  the  same  provision  precisely.  Surrounding  the  embryo, 
there  is  laid  up  a  store  of  formed  material  for  the  nourish- 
ment of  the  young  plant  until  such  a  time  as  it  shall  have  de- 
veloped its  roots  and  leaves,  the  organs  by  which  it  gathers  its 
food,  sufficiently  for  this  purpose. 

In  neither  of  these  is  the  food  material  in  a  condition  to  be 
formed  into  the  tissues  of  the  young  animator  plant,  without 
remoleculization.  It  must  be  redigested  before  it  can  be 
assimilated  by  the  embryo.  This  process  has  been  best 
studied  in  the  seed.  Here  it  is  found  that  the  embryo  elimi- 
nates a  true  digestive  substance,  called  diastase,  the  office  of 
which  is  the  digestion  of  the  store  of  food  material.  Of  this 
substance  Regnault  says  :  "  A  peculiar  nitrogenous  substance, 
called  i  diastase/  which  possesses  the  property  of  converting  a 
large  proportion  of  fecula  (starch)  into  dextrin,  and  even  into 
sugar,  when  its  action  is  sufficiently  prolonged,  exists  in  the 
germ  of  the  cerealia  and  in  tubercular  vegetables.  It  appears 
to  be  formed  at  the  moment  of  germination,  probably  at  the 
expense  of  the  albuminous  matter  contained  in  the  grain,  as 
it  resides  in  the  very  origin  of  the  germ,  and  in  the  eye  of  the 
tuber;  and  its  use  in  the  vegetable  economy  appears  to  be 
that  of  disaggregating  the  amylaceous  matter,  and  transform- 
ing it  into  an  isomeric  soluble  substance,  which  the  vital 
forces  then  change  into  other  isomeric,  but  insoluble  sub- 
stances, such  as  cellulose,  which  is  to  form  the  framework  of 
the  growing  plant." 

This  substance  is  very  well  known,  and  its  action  on  the 
starch  has  been  closely  studied.  It  may  be  precipitated  by 
alcohol,  and  obtained  in  the  form  of  a  powder,  and  preserved 
fora  long  time,  and  when  redissolved  in  water  will  still  pro- 
duce its  effect  on  starch.  This  effect,  like  that  of  other  sol- 
uble ferments,  is  not  to  be  explained  by  the  ordinary  chemical 
laws.  One  part  of  diastase  will  convert  2000  parts  of  starch 


SPROUTING   OF   SEEDS.  93 

into  sugar.  The  office  of  this  substance,  therefore  becomes 
clear;  it  is  the  true  digestive  body  of  the  embryo  plant,  by 
which  its  store  of  food  material  is  remoleculized  and  fitted 
for  its  assimilation. 

In  the  egg,  this  process  has  not  been  so  well  made  out;  but 
enough  is  known  to  determine  the  fact  that  the  store  of  albu- 
men is  profoundly  changed  previous  to  assimilation. 

The  perennial  plant,  which  lies  dormant  in  winter,  is  to 
some  extent  similar,  during  the  interval  of  inactivity,  to  the 
seed.  It  contains  within  its  structure  formed  material  for 
use  in  spring  time,  for  the  reformation  of  the  leaves,  for  the 
gathering  and  transformation  of  a  portion  of  its  food  material. 
These  stores  of  formed  material  seem  to  be  made  use  of  much 
in  the  same  manner,  and  by  the  same  means,  by  which  they 
are  transformed  in  the  seed ;  that  is,  by  means  of  a  diastase, 
or  soluble  ferment,  formed  at  the  proper  moment  for  its  solu- 
tion. In  this  respect,  we  find  a  close  analogy  between  the 
plant  and  the  animal,  as  we  shall  see  further  on. 

I  have  brought  forward  these  well-known  phenomena  for 
the  purpose  of  enforcing  the  principle  lying  at  the  very 
threshold  of  the  nutritive  function ;  for  the  purpose  of  impress- 
ing the  fact  that  the  life  force,  wherever  found,  carries  forward 
its  business  in  regular  and  definite  forms,  by  regular  and  defi- 
nite means ;  and  that  its  means  to  the  accomplishment  of  the 
preparation  of  its  food  material  is  similar  throughout  all  its 
varied  forms.  One  form  of  life  lives  on  this,  another  on  that 
food  material,  but  the  process  by  which  food  material  is 
brought  into  a  state  fitting  it  for  its  final  assimilation  by  the 
life  force,  and  the  building  of  tissue,  of  whatever  kind  or 
quality,  is  the  same  in  its  general  plan. 


94  THE   GERM   THEORY   OF   DISEASE. 

NUTEITION. 

The  digestion  of  nutrition  is  performed  by  the  tissue  itself. 
When  no  ferment  substance  is  divisible  from  the  tissue  the 
existence  of  such  substance  has  been  inferred  from  the  phe- 
nomena observed.  We  think  no  one  will  doubt  that  the  food 
of  the  animal  goes  through  further  fermentation  or  digestion 
after  it  is  taken  into  the  blood,  at  least,  a  certain  remoleculi- 
zation,  by  whatever  name  it  may  be  called.  Is  this  change 
brought  about  in  the  blood  ?  Posssibly  it  is,  to  some  extent, 
especially  during  its  passage  through  the  liver,  the  great  gland 
of  the  blood  vascular  system,  the  soluble  ferment,  or  diastase, 
of  which  is  well  known.  But  the  great  change  is  brought 
about  by  the  tissues  themselves. 

In  primary  digestion  there  is  simply  an  absorption  of  other 
molecules  or  atoms,  by  the  molecule  of  the  substance  under- 
going digestion,  or  a  splitting  up  into  simpler  compounds.  In 
the  nutritive  digestion  (nutrition  assimilation)  there  is  a 
reorganization  of  the  elements  into  new  tissue  and  formed 
material.  This  reorganization  is  performed  in  the  cells  them- 
selves. The  substances  are  taken  into  the  interior  of  the  cells 
by  osmosis,  and  then  remoleculized  by  act  of  the  vital  force. 
This  is  the  point,  evidently,  of  the  most  intimate  association 
of  matter  with  life;  it  is  here  that  matter  is  said  to  be  en- 
dowed with  life. 

The  products  formed  here  are  very  definite.  The  reorgani- 
zation results  in  tissue,  each  tissue  selecting  and  building  for 
itself,  and  to  itself,  from  the  material  carried  in  the  blood 
streams,  obtained  from  the  primary  digestion  and  from  the 
lungs.  In  this  reorganization  and  building  by  the  tissues, 
definite  waste  products  are  given  back  to  the  blood  streams, 
namely,  carbonic  acid  and  urea.  These  are  cast  out  by  the 
lungs  and  kidneys.  They  are  found  to  be  incompatible  with 


NUTRITION.  95 

life,  if  retained  in  any  considerable  quantity.  Here,  also,  are 
formed  the  secretions  destined  to  serve  the  animal  in  the  per- 
formance of  the  digestive  and  other  functions ;  in  the  animal 
forms  mostly  by  specialized  cells  acting  vicariously  for  the 
other  tissues  of  the  body.  These  are  special  developments  of 
function,  seen  as  we  ascend  the  scale  of  life.  But  these  func- 
tions are  also  present  in  the  unicellular  forms  of  life,  where 
there  is  no  such  division  of  labor  or  function  developed.  It 
is  not  a  new  function,  but  a  special  development  of  cells  to 
act  in  this  matter  for  the  whole. 


FIFTH  LECTURE. 

YEAST  PLANT. 

For  comparison,  let  us  turn  again  to  the  yeast  plant.  Here 
we  have  no  blood  streams  to  interfere  with  our  study  of  phe- 
nomena. The  same  cells  that  emit  the  soluble  ferment  which 
performs  the  primary  digestion,  appropriate  the  results  of  that 
digestion,  not  individually,  but  en  masse.  That  is,  each  cell 
individually  excretes,  so  to  speak,  the  material,  the  soluble 
ferment,  that  performs  primary  digestion.  This  digestion  is 
performed  by  the  whole  amount  of  material  excreted,  inde- 
pendently of  the  individual  cell,  but  in  the  appropriation  of 
the  results  of  this  primary  digestion,  each  individual  cell  acts 
for  itself  only,  and  independently  of  all  other  cells.  The 
result  is  the  building  up  of  the  tissue  of  the  cells  by  remolecu- 
lizing  the  original  elements  into  new  forms,  with  the  elimi- 
nation of  waste  products. 

In  this  case  the  waste  products  are  alcohol  and  carbonic 
acid.  One  is  the  same  as  in  the  animal,  carbonic  acid,  the 
other  is  different.  These  waste  products  agree,  in  their  eifects 
upon  the  activity  of  the  plant,  with  the  waste  products  of  the 
animal  upon  its  life  force.  Alcohol,  in  a  certain  quantity, 
stops  the  growth,  the  activity,  of  the  yeast  plant  which  pro- 
duced it,  and  if  sufficiently  concentrated,  destroys  it.  Urea 
does  the  same  for  animal  life. 

These  excretory  products  differ  widely  among  the  lower 
forms  of  life,  and  yet,  as  we  shall  show  in  another  lecture,  re- 
tain a  constant  resemblance. 

In  case  of  the  mycodermi  aceti,  the  acetic  acid  plant,  the 
excretory  products  are  carbonic  acid  and  acetic  acid.  With 

96 


YEAST   PLANT.  97 

the  bacteria  termo,  the  excretory  products  are  very  complex, 
consisting  of  ammonia,  sulphuretted  hydrogen,  and  other  ill- 
smelling  products  of  putrefactive  fermentation.  Some  of  the 
mucidines  excrete  butyric  acid;  other  forms  excrete  other 
waste  products.  Only  a  few  of  these  have,  as  yet,  been  very 
accurately  studied. 

Often,  perhaps,  it  is  by  these  excretory  products  from  bacte- 
ria that  gain  access  to  the  blood,  and  are  capable  of  living 
there,  that  disease  is  produced.  One  case  in  point.  Dr.  Car- 
ter, of  India,  in  his  very  careful  and  laborious  examination 
of  the  blood  spirillum  of  relapsing  fever,  has  found  that  these 
organisms  become  still,  and  diminish  in  number  during  the 
exacerbation  of  the  fever,  and  during  the  intervals  of  com- 
parative freedom  from  the  rigor  of  the  disease  they  become 
active  and  augment  in  numbers,  until  the  approach  of  another 
attack  of  fever.  What  does  this  mean?  Certainly  the 
disease  is  not  caused  in  this  case  by  the  primary  digestion,  by 
the  soluble  ferment,  as  it  seems  to  be  in  hospital  gangrene. 

The  case  seems  reversed.  Here  it  seems  that  the  accumu- 
lation of  the  excretory  products  of  the  organisms  cause  the 
sickness ;  also,  that  the  amount  present  in  the  blood  is  suffi- 
cient to  check  the  development  of  the  organism.  Suppose  the 
yeast  plant  could  grow  in  the  blood,  and  develop  its  alcohol, 
might  it  not  intoxicate  the  man  ? 

The  course  seems  to  be  this.  The  soluble  ferment  excreted 
by  the  spirillum  affects  the  patient  but  little,  the  development 
proceeds,  and  excretory  products  begin  to  accumulate  more 
rapidly  than  they  are  carried  away  by  the  emunctories ;  finally, 
when  a  certain  concentration  has  been  reached,  the  patient  is 
thrown  into  violent  fever.  The  bacteria  are  also  so  affected 
by  their  own  excreta  that  they  droop  and  fail  to  flourish. 
They  become  quiet.  The  patient  eliminates  the  poison,  and 
all  is  well  again  with  both  patient  and  spirillum,  and  the 


98  THE   GERM   THEORY   OF   DISEASE. 

repetitions  continue.     But  in  this  I  am  anticipating ;  waste 
products  will  be  discussed  in  another  lecture. 

CELLULAR  DIGESTION  IN  THE  HIGHER 
ANIMALS. 

In  the  higher  forms  of  life  we  find  a  division  of  labor  in 
the  primary  portions  of  the  nutritive  function,  the  prepara- 
tion of  the  material  for  nutrition.  Certain  portions  of  the 
animal  body  are  set  apart,  so  to  speak,  to  perform  this  func- 
tion for  the  whole.  In  the  lower  forms  this  function  is 
performed  by  the  whole  mass  of  cells  as  a  unit,  each  doing  a 
part  as  an  element  of  the  mass.  In  proof  of  this  we  have 
cited  the  instance  of  the  bacterium,  in  blood,  where  digestion 
can  only  be  accomplished  by  the  united  efforts  of  a  mass  of 
cells.  We  find,  then,  that  in  the  lower  forms  of  life  cells 
may  act  for  each  other  in  the  matter  of  primary  digestion, 
and  that  in  the  higher  forms  of  life  a  special  development 
occurs  which  enables  certain  cells  to  act  for  the  general  mass. 
But  in  the  matter  of  nutritive  digestion  each  individual  cell 
must  act  for  itself  in  the  one  case,  as  in  the  other.  Here 
there  can,  in  the  very  nature  of  things,  be  no  vicarious 
function. 

Is  it  impossible  that  the  cells  of  the  higher  animals  may 
excrete  digestive  fluids ;  soluble  ferments,  also,  under  certain 
particular  circumstances?  We  shall  see. 

RESORPTIVE  DIGESTION. 

We  now  approach  an  important  point  in  this  discussion, 
the  third  form,  or  resorptive  digestion. 

We  wish  to  state  distinctly  that  all  resorptiori  and  absorp- 
tion of  material  not  primarily  fluid,  that  is,  not  simply  en- 
dosmotic,  is  of  the  same  nature  as  primary  digestion,  and  is 
performed  in  a  similar  manner  and  by  similar  agencies, 


RESOKPTIVE   DIGESTION.  99 

through  a  vicarious  secretion  of  a  digestive  fluid,  a  soluble 
ferment,  by  the  proper  tissues  of  the  body. 

We  will  take  for  illustration  the  familiar  process  of  the 
resorption  of  the  .roots  of  the  temporary  teeth.  This  is  a 
physiological  process,  as  all  other  resorptive  processes  are. 
It  is  brought  about  by  the  action  of  certain  cells  which  have 
become  known  as  osteo-  or  odontoclasts.  It  has  been  claimed 
that  the  osteoclasts  are  really  osteoblasts,  that  have  changed 
their  function  from  that  of  builders  of  bone  to  absorbents  of 
bone.  The  distinction  is  not  important  in  this  lecture.  These 
may  be  only  the  ordinary  connective  tissue  cells  of  the  part  in 
immediate  proximity  with  the  part  to  be  removed,  which  have 
temporarily  taken  on  new  functions,  the  secretion  or  elabora- 
tion of  a  soluble  ferment  for  the  removal  of  the  roots  of  those 
teeth  which  are  no  longer  wanted.  These  cells  perform  this 
act  in  an  indirect  manner.  It  is  plain  that  these  roots  are  not 
removed  by  any  mere  mechanical  force.  These  cells  have  no 
physical  power  of  gnawing  into  them.  They  secrete  a  soluble 
ferment,  or  analogous  body,  which  digests  them,  breaks  them 
down,  and  fits  their  material  for  entrance  into  the  blood 
streams  by  osmosis,  just  as  solid  ingesta  in  the  stomach  is 
broken  down  and  fitted  to  enter  the  circulation  by  osmosis. 
There  seems  to  be  no  foundation  for  the  notion  that  the  re- 
sorbed  product  of  these  roots  may  not  form  proper  pabulum 
for  the  building  up  of  other  tissues;  that  the  absorbed  product 
is  necessarily  excreted.  Resorption  is  not  a  process  for  the 
forming  of  waste  products. 

As  this  process  has  been  pretty  closely  studied,  we  will 
examine  it  a  little  further.  From  decay  and  other  accident 
the  temporary  teeth  are  very  liable  to  lose  their  pulps,  which 
very  often,  we  may  say  generally,  results  in  the  formation  of 
alveolar  abscess  at  the  apex  of  their  roots.  If  such  an  abscess 
exists  at  the  time  the  resorption  should  take  place,  such  re- 


100  THE   GERM   THEORY   OF   DISEASE. 

sorption  fails,  partially  or  entirely.  The  tissue  which  should 
perform  this  function  is  thrown  into  a  pathological  state,  and 
the  secretion  of  the  soluble  ferment  does  not  take  place  in  the 
normal  manner.  If,  however,  the  abscess  «does  not  occur,  or 
if  such  abscess  be  cured,  and  the  tissue  in  immediate  proximity 
to  such  devitalized  root  be  perfectly  healthy,  it  is  found  that 
the  resorption  of  the  root  goes  on  in  a  normal  manner.  The 
mere  death  of  the  root  does  not  interfere  with  resorption, 
provided  a  physiological  condition  is  maintained  in  the  imme- 
diately surrounding  cells,  which  are  the  active  agents  in  the 
work.  The  soluble  ferment  does  not  depend  for  its  action 
upon  the  life  of  the  tissue  to  be  acted  upon.  The  roots  of  the 
teeth  are  simply  digested,  and  enter  the  blood  streams  by 
osmosis,  as  any  other  digested  material.  Nothing  more,  nor 
less. 

DIGESTION  OF  BLOOD  CLOT. 

What  happens  when  an  injury  occurs,  and  a  blood  clot  is 
formed  within  the  tissues?  Is  such  a  blood  clot  a  living  sub- 
stance? Certainly  that  cannot  be  maintained.  But  it  becomes 
organized.  How?  Certainly  the  blood  clot,  as  such,  does 
not  itself  become  living  tissue. 

The  process  occurring  here,  by  which  the  clot  is  removed, 
is  similar  in  kind  to  that  of  digestion — is  digestion.  All 
around  it,  the  connective  tissue  cells  begin  to  throw  out  a 
soluble  ferment,  by  which  the  substance  of  the  clot  is  dis- 
solved and  begins  to  pass  into  the  blood  streams  by  osmosis. 
Young  cells  wander  out  into  the  liquefying  clot  in  all  direc- 
tions, grow,  and  furnish  their  quota  of  fresh  increment  of 
ferment  substance  to  liquefy  the  clot.  The  question  as  to 
whether  any  of  the  blood  cells  (white  blood  corpuscles)  be- 
come connective  tissue  cells  under  these  conditions,  need  not 
be  argued  pro  nor  con  here,  for  it  does  not  affect  our  present 
purpose.  Certain  it  is  that  cells  are  found  growing  out  into 


DIGESTION   OF   LIGATURES.  101 

the  clot,  and  acting  very  like  some  of  the  forms  of  bacteria. 
Thus,  the  clot  is  digested  and  removed,  and  when  it  is  gone 
any  surplus  new  tissue  that  may  have  been  formed  during  the 
activity  of  the  process  suffers  the  same  fate.  It  is,  in  turn, 
digested  and  removed. 

DIGESTION  OF  LIGATURES. 

Of  late  it  has  become  quite  the  fashion,  among  surgeons,  to 
use  ligatures,  for  deep  sutures,  made  of  digestible  material, 
such  as  catgut,  animal  membrane,  etc.  These  are  left  in,  and 
it  is  said  they  are  absorbed.  They  must  be  dissolved  first. 
They  do  not  dissolve  in  ordinary  liquids,  nor  do  they  dissolve 
in  pus,  or  upon  pus-forming  surfaces,  or  in  the  usual  plasma 
of  the  tissues.  The  surgeon  is  very  careful  that  they  be  so 
prepared  that  they  shall  not.  He  is  careful  that  they  are  not 
easy  of  digestion.  The  "  International  Encyclopedia  of  Sur- 
gery "  says:  " The  spontaneous  solution  of  catgut  ligatures, 
when  set  in  wounds,  is  caused,  not  by  any  chemical  solution 
of  their  structure,  nor  by  any  process  of  organization  which 
they  undergo,  but  by  the  invasion  of  leucocytes,  under  the 
operation  of  which  they  vanish,  while  new  tissue  takes  their 
place;  but,  if  they  be  over-prepared  (i.  e.y  rendered  too  diffi- 
cult of  digestion),  this  change  does  not  occur,  and  they  act  like 
foreign  bodies  in  general." 

Here  we  see  that  the  ligature  does  not  dissolve  in  the  ordi- 
nary plasma  of  the  tissue,  if  properly  prepared.  The  tissue 
must  approach  closely  a  physiological  condition,  it  must  throw 
out  certain  cells  which  invade  it,  as  it  would  be  invaded  by 
bacteria  if  they  had  the  opportunity.  These  cells  must  throw 
out  their  special  ferment  for  the  occasion,  to  digest  the  catgut 
and  make  room  for  themselves,  as  would  be  done  by  bacteria ; 
and  thus  they  continue  to  dissolve  out  the  foreign  digestible 
substance  and  take  its  place,  stimulated  to  this  action  by  its 


102  THE   GERM   THEORY   OF   DISEASE. 

presence.  If,  however,  the  substance  is  too  difficult  of  diges- 
tion, over-stimulation  results,  and  instead  of  the  soluble  fer- 
ment being  formed,  the  cells  degenerate,  pus  forms,  and  the 
process  fails. 

DIGESTION  OF  SPONGE. 

Let  us  examine  the  operation  of  the  sponge  graft.  In  the 
sponge,  as  prepared  for  this  operation,  we  have  a  material 
somewhat  difficult  of  digestion,  a  material  that  would  be  very 
slowly  acted  upon  by  the  gastric  juice.  From  this  circum- 
stance, and  the  fact  of  its  very  minute  porosity,  it  has,  hap- 
pily, been  selected  for  the  purpose  of  inducing  granulations 
for  the  filling  out  of  lost  tissues.  What  may  have  led  to  this 
selection  I  am  not  informed.  It  was  probably  directed  by 
some  accidental  observation.  The  fact,  however,  is  now  well 
established,  that  the  tissues  are  stimulated,  by  its  presence,  to 
fill  its  pores  with  granulations,  after  which  the  sponge  itself 
gradually  disappears,  leaving  the  opening  filled  with  new 
tissue. 

The  physiological  phenomena  may  be  thus  explained :  as 
lias  been  said,  the  tissue  is  stimulated  by  the  presence  of  the 
sponge,  and  granulation  proceeds  actively.  At  the  same  time 
a  soluble  ferment  is  thrown  out,  by  whicli  those  portions  of 
sponge  inclosed  in  the  matrix  of  granulations  are  slowly  di- 
gested and  pass  off  by  osmosis.  At  the  same  time,  the  granu- 
lations crowd  into  the  space  gainec}.  This  process  continues 
regularly,  until  every  particle  of  the  sponge  is  removed,  and 
its  place  supplied  by  living  tissue.  I  think  it  will  be  clear  to 
every  one,  especially  to  every  surgeon,  that  this  sponge  does 
not  dissolve  in  the  ordinary  plasma  of  the  blood,  or  tissues. 
The  tissues  are  stimulated  to  an  extraordinary  proliferation  of 
cells  by  its  presence.  They  are  also  stimulated  to  the  secre- 
tion of  a  soluble  ferment,  suitable  for  its  digestion  and  re- 
moval. 


DIGESTION   OF   SPONGE.  103 

The  same  process  precisely  is  called  out  in  the  absorption 
of  the  catgut  ligature,  which  is  progressively  invaded  by  leu- 
cocytes, which  digest  the  foreign  substance  and  remove  it  by 
osmosis,  making  room  for  themselves,  much  as  would  be  done 
by  bacteria,  and  when  the  ligature  is  gone  we  have  a  cord  of 
new  living  tissue  in  its  stead.  Even  ivory  driven  into  the 
flesh  is  eaten  into,  digested,  and  portions  removed,  by  the  in- 
vasion of  leucocytes. 

It  will  be  noticed  here,  as  everywhere,  when  this  kind  of 
digestion  occurs,  the  tissue  is  applied  directly  to  the  substance 
to  be  digested,  and  invades  its  substance  as  digestion  makes 
room  for  its  growth,  so  that  the  tissue  is  continuously  in  in- 
timate relation  with  it,  progressively  invades  it.  We  do  not 
suppose  that  this  soluble  ferment  is  pepsin,  but  a  body  pecu- 
liar to  the  connective  tissues,  formed  only  in  connection  with  a 
foreign  substance. 

We  will  suggest  that  the  sponge  graft  offers  the  most  fea- 
sible means  of  isolating  this  peculiar  ferment.  If  several 
sponge  grafts  were  placed  in  suitable  animals,  as  dogs,  and 
the  animals  killed  at  a  proper  time,  and  the  grafts  immediately 
treated  in  some  way  similar  to  that  employed  for  obtaining 
pepsin  from  the  gastric  mucous  membrane  of  the  pig,  this  fer- 
ment wTould  doubtless  be  found.  The  process  would  perhaps 
require  to  be  varied  somewhat  to  suit  the  different  character 
of  the  soluble  ferment.  If  this  soluble  ferment  could  be  had 
in  sufficient  amount  and  purity,  it  would  be  of  some  value  in 
testing  the  different  substances  suggested  for  ligatures,  etc., 
and  possibly  in  ways  not  now  thought  of.  But  the  principal 
use  of  the  proceeding  would  be  the  demonstration  of  a  physio- 
logical process,  and  the  extension  of  exact  knowledge.  Such 
a  demonstration  would  furnish  a  new  basis  of  fact  from  which 
thought  might  radiate  to  the  unfolding  of  still  other  facts,  no 
less  important. 


104  THE   GERM   THEORY   OF   DISEASE. 

NECROSED  BONE. 

Take  the  case  of  necrosed  bone.  How  is  a  sequestrum 
formed,  but  by  the  digestion  and  removal  of  that  portion 
which  connects  it  with  the  living  bone.  Can  this  be  accom- 
plished by  any  of  the  more  ordinary  fluids  found  in  the 
tissues  ?  certainly  not.  Then  a  special  menstruum  is  formed 
for  the  purpose  of  this  solution.  Formed  where,  and  by  what  ? 
Not  in  some  distant  part  and  sent  here,  but  by  the  tissues  in 
immediate  contact,  acting  by  virtue  of  their  natural  endow- 
ments and  the  stimulus  of  juxtaposition  with  an  undesirable 
substance.  If  the  tissue  could  act  without  undue  irritation, 
the  act  of  digestion  of  the  part  should  occur,  and  its  place 
be  supplied,  without  the  formation  of  pus.  However,  this 
probably  never  occurs,  except  in  cases  of  the  death  of  very 
small  portions  of  bone.  In  some  cases,  however,  we  believe  it 
does  occur  to  a  considerable  extent.  We  have  witnessed  cases 
of  healing  of  wounds  involving  bone,  which  we  can  explain  in 
no  other  way.  In  most  cases,  however,  the  inflammation  runs 
so  high,  and  continues  so  long,  that  pus  forms,  and  prevents  the 
physiological  action  of  the  cells.  These  cells  cannot  perform 
this  function  from  a  distance.  The  ferment  substance,  if 
formed,  is  dissipated  in  the  fluids;  they  must  be  in  juxtaposition 
with  the  substance  to  be  digested,  or  at  least,  no  dissipating  men- 
struum must  intervene,  in  order  that  the  integrity  of  the  soluble 
ferment  may  be  preserved  and  applied  directly  to  its  work. 

If  this  condition  can  be  attained,  dead  bone  will  be  digested 
and  removed.  As  a  matter  of  fact,  we  generally  find  sequestra 
eaten  into,  here  and  there,  sometimes  more,  sometimes  less. 
These  burrowings  represent  points  where  the  granulations,  in 
a  state  closely  approximating  healthy  action,  have  come  in 
contact  with  and  invaded  the  dead  bone.  If  this  condition 
could  be  maintained  at  all  points,  the  sequestrum  would  be 
completely  removed. 


ACTION    OF   TISSUES.  105 

Krause  (Algemeine  U.  Microscopische  Anatomic,  S.  74), 
examines  the  osteoclasts  very  closely,  and  the  manner  in  which 
living  bone  is  removed  by  them.  He  is  of  the  opinion  that 
they  furnish  a  secretion  for  this  purpose,  and  thinks  it  con- 
tains lactic  acid.  He  says,  ivory  driven  into  the  flesh  is 
absorbed  by  them,  and  that  the  osteoclasts  are  found  in  the 
pits  formed  in  it,  as  in  living  bone  that  is  undergoing  this 
process;  and  quotes  Kolliker,  Billroth,  De  Morgan  and 
Tomes,  as  authority.  These  osteoclasts  must  be  formed  from 
the  ordinary  connective  tissue  cells,  or  leucocytes.  Not  from 
osteoblasts. 

ACTION  OF  TISSUES. 

Absorption  under  pressure  is  in  no  wise  different  from  any 
other  process  of  absorption.  A  certain  portion  of  the  cells, 
crowded,  but  not  too  much,  take  upon  themselves  a  new 
action  and  develop  a  ferment  which  destroys  their  neighbors 
less  favorably  placed.  It  is  well  known  that  under  pressure, 
certain  tissues  are  destroyed  in  preference  to  others.  This 
would  be  a  very  interesting  field  of  research,  but  we  have  not 
time  to  enter  it  in  this  lecture. 


This  we  conceive  to  be  the  normal  action  of  the  tissues  of 
the  higher  animals.  How  do  the  lower  forms  of  life  differ 
from  these?  In  the  vegetative  sense,  the  difference  is  but 
slight.  They  differ  widely  in  formative  power.  In  the  very 
low  forms  the  cells  fall  apart  instead  of  aggregating  and 
unifying  into  more  complex  compound  forms.  In  this  sense 
there  is  a  wide  physiological  difference,  but  in  the  matter  of 
digestion,  nutrition,  and  the  formation  of  waste  products,  the 
similarity  is  very  close. 


106  THE   GERM   THEORY   OF   DISEASE. 

SOLUBLE   FERMENTS. 

We  have  said  enough  to  indicate  the  mode  of  action  of 
bacteria  in  destroying  substances  in  general,  and  in  causing 
disease.  Some  forms  may  possibly  cause  disease  by  their 
presence,  by  aggregating  into  groups  and  causing  irritation, 
like  the  animal  parasites,  as  the  itch  mite;  but  we  are  per- 
suaded that  their  general  mode  of  action  is  through  their 
soluble  ferment  and  the  toxic  properties  of  their  waste  pro- 
ducts, to  be  examined  presently.  In  this  manner  the  hardest 
substances  are  made  to  yield ;  are  melted  down  almost  as 
readily  as  softer  materials.  Soluble  ferments  do  not  depend 
for  their  dissolving  power  upon  either  acidity  or  alkalinity. 
Some  are  acid,  but  generally  these  reactions  are  not  very 
marked,  and  normally  seem  capable  of  considerable  variation. 
They  seem  to  be  Nature's  solvents,  manufactured  by  the  life 
force,  and  used  for  the  maintenance  of  the  creature.  We  can 
neither  form  them,  nor  tell  why  they  should  have  such  power. 
We  can  only  examine  them,  learn  their  powers,  and  wonder 
at  Nature's  handiwork. 

PATHOLOGICAL  FORMATION    OF    FERMENTS. 

We  have  reason  to  believe,  at  least  to  suspect,  that  soluble 
ferments  are  often  formed  in  places  where  they  are  not  wanted. 
Tissue  is  stimulated  to  false  secretion  by  various  irritants  and 
in  many  ways.  It  is  probable  that  many  of  the  excoriating 
secretions  which  we  see  about  the  ears,  necks,  and  other  parts, 
in  children,  are  soluble  ferments  given  out  through  some  mal- 
condition  of  the  tissues.  In  this  manner  much  harm  is  accom- 
plished. We  will  allude  to  this  again. 

We  have  reason  to  suspect  that  in  some  cases  decay  of  the 
teeth  may  come  about  in  this  way.  We  have  already  seen 
that  tooth  substance  is  digested  and  removed  by  a  soluble 
ferment  normally  formed.  Why  is  riot  the  tissue  forming  a 


PATHOLOGICAL  FORMATION  OF  FERMENTS.     107 

soluble  ferment  dissolved  by  it  ?  The  answer  is  this :  Any 
tissue  forming  a  soluble  ferment  is  protected  from  the  action 
of  such  ferment  substance  by  the  life  force.  This  answer  is 
very  clear,  and  is  undoubtedly  a  general  fact.  But  what  is  life 
force  ?  Here  we  are  more  or  less  bewildered,  for  the  want  of 
more  exact  knowledge.  It  is  well  known  that  the  mucous 
membrane  of  the  stomach  of  a  dead  dog  is  readily  digested 
by  the  gastric  juice  of  a  living  dog.  Not  only  this;  but  the 
gastric  juice  in  the  stomach  will,  after  death,  digest  the  mucous 
membrane  which  formed  it.  In  this  direction  there  is  a  very 
perfect  chain  of  fact,  fully  establishing  the  protective  power 
of  the  life  force. 

These  ferments  are,  however,  constantly  brought  in  contact 
with  tissues  which  do  not  form  them,  such  as  the  ducts  of  the 
glands  and  other  surfaces  over  which  they  may  be  spread. 
This  fact  might  lead  to  an  extension  of  our  answer.  Might 
lead  us  to  say  that  all  living  tissues  are  protected  from  the 
solvent  action  of  the  soluble  ferments. 

This  statement,  however,  goes  too  far.  Certainly  it  cannot 
be  maintained  that  the  roots  of  the  temporary  teeth  must  die 
before  resorption  takes  place. 

Again ;  the  tissues  forming  the  gums  and  mucous  membrane 
in  advance  of  the  erupting  tooth  are  removed  by  this  same 
process.  It  cannot  be  claimed  that  they  are  dead  tissues. 
Very  many  other  instances  of  the  same  nature  might  be  cited. 
Then  it  is  not  true  that  all  living  tissues  are  protected  from 
this  digestion  by  the  vital  principle.  Hence,  we  are  driven 
back  upon  our  first  statement,  i.  e.,  that  any  tissue  forming  a 
soluble  ferment  is  protected  from  the  action  of  such  ferment 
substance  by  the  life  force.  Other  tissues  are  not  so  protected. 
We  may  infer  that  the  tissue  forming  the  lining  membranes 
of  the  ducts  of  glands,  and  any  normal  receptacle  of  such 
a  fluid,  would  be  protected  from  its  action,  just  as  the  tissue 
6 


108  THE   GERM   THEORY   OF   DISEASE. 

forming  the  secretion.  But  it  is  plain  that  other  tissues  are 
not  so  protected,  or,  if  so  protected,  that  protection  is  in  some 
way  withdrawn,  under  special  circumstances.  How?  The 
nerve  force  suggests  itself;  but  this  hypothesis  presents  serious 
difficulties.  It  seems  much  more  probable  that  the  explana- 
tion is  to  be  found  in  the  development  of  the  power  of  form- 
ing the  soluble  ferment,  than  in  the  withdrawal  of  the  power 
of  resisting  it.  In  all  cases  in  which  I  have  personally  made 
examination  of  the  tissue  advanced  against  resorbed  surfaces, 
surfaces  being  removed,  I  have  found  a  marked  change  in  the 
general  appearance  of  the  tissue.  It  has  taken  on  the  appear- 
ance, more  or  less,  of  granulating  tissue,  and  these  changed 
cells  have  received  the  name  of  osteoclasts,  odontoclasts,  etc., 
according  to  their  location  and  purpose.  The  fact  that  this 
peculiar  development  is  the  accompaniment  of  resorption  of 
bone,  roots  of  teeth,  etc.,  is  universally  recognized,  I  believe, 
by  histologists.  The  inference,  then,  that  this  solvent-form- 
ing power  is  a  special  development,  would  seem  to  be  main- 
tained. We  conclude  that  this  special  soluble  ferment  is  only 
formed  under  special  circumstances.  Physiologically,  only 
in  case  some  tissue  not  wanted  longer  is  to  be  removed ;  as 
bone  during  growth,  and  consequent  change  of  form,  roots  of 
temporary  teeth  at  shedding  time,  or  when  some  foreign 
substance  has  been  lodged  in  the  tissue.  Pathologically, 
through  some  irritation  or  other  abnormal  condition,  the  tissue 
is  induced  to  a  false  action.  We  can  understand  that  the  pres- 
ence of  a  substance,  such  as  a  catgut  ligature  or  a  sponge, 
should  induce  some  special  action  of  the  tissue,  through  which 
it  would  be  freed  from  its  presence.  But  how  the  same 
phenomena  should  be  called  into  play  for  the  removal  of 
parts  of  bone  during  growth,  for  the  purpose  of  rendering 
them  symmetrical  and  perfecting  their  form,  is  more  difficult 
of  comprehension.  Take,  for  instance,  the  phenomena  of  the 


PATHOLOGICAL  FORMATION  OF  FERMENTS.     109 

growth  of  the  lower  jaw.  In  the  child  of  five  years  its  body 
is  short,  just  long  enough  to  accommodate  the  ten  deciduous 
teeth.  A  lengthening  of  the  body  of  the  bone  occurs,  to  make 
room  for  three  large  permanent  molars  on  each  side.  In  this 
lengthening  the  ramus  of  the  jaw  is  carried  back  about  one 
and  a  half  inches,  which,  in  effect,  protrudes  the  lower  jaw 
forward.  Now  this  is  not  an  interstitial  growth  of  the 
bone  ;  but  the  ramus  is  resorbed  away  from  its  anterior  aspect 
and  built  up  posteriorly.  The  osteoclast  cells,  soluble  fer- 
ment-forming cells,  are  found  there,  and  their  effects  upon 
the  bone  may  be  seen.  Their  work,  in  this  instance,  however, 
is  done  quite  evenly  and  smoothly.  This  is  the  type  of  all 
changes  of  form  in  the  osseous  system.  It  will  be  seen  at 
once  that  the  amount  of  this  work  done  during  the  growth, 
formative  stage,  of  the  osseous  system  is  simply  immense. 
The  head  of  each  bone  must  be  trimmed  down  to  the  size  of 
the  shaft  as  the  bone  lengthens,  etc. 

By  what  power  is  this  action  controlled  ?  Here  we  come 
directly  upon  the  unknown.  If  we  say  it  is  through  the  con- 
trol of  the  nervous  system,  we  will  be  brought  face  to  face 
with  the  symmetrical  formation  of  bones  in  the  foetus,  in 
which  the  formation  of  a  nervous  system  has  failed,  in  which 
the  spinal  canal,  or  groove,  has  never  closed,  is  open  from  end 
to  end,  and  no  trace  of  nerves  is  to  be  found.  Yet,  such  a 
foetus  has,  with  the  exception  of  the  spinal  column  and  skull- 
bones,  developed  to  term,  a  perfectly  symmetrical  skeleton. 
After  seeing  this,  the  idea  that  these  processes  are  under  the 
control  of  the  nervous  system  seems  untenable.  And  I  am 
free  to  say  that  I  have  no  hypothesis  to  advance,  except  to 
say  that  they  are  under  the  control  of  the  life  force,  which, 
I  confess,  is  no  explanation. 


110  THE   GERM   THEORY   OF   DISEASE. 

PARASITES. 

After  what  I  have  said,  the  examples  I  have  given,  it  seems 
plain  that  the  work  of  these  lowly  forms  of  life  is  to  cause  a 
remoleculization  of  the  substances  with  which  they  come  in 
contact. 

This  power  of  remoleculization  of  certain  forms  of  matter 
is  one  of  the  especial  physical  attributes  of  the  life  force.  It 
is  the  one  great  power  upon  which  life  depends  for  its  con- 
tinued existence.  No  form  of  life  can  continue  to  exist  with- 
out itself  exhibiting  this  power,  or  borrowing  directly  from  a 
form  of  life  that  does  exhibit  it  in  a  marked  degree.  (It  is 
claimed  that  certain  forms  of  parasitic  plants  draw  from  and 
appropriate  to  themselves  food  material  which  has  been  assimi- 
lated by  their  host.  Even  here  it  is  most  probable  that  there 
is  a  form  of  remoleculization.) 

Now,  in  case  of  parasitic  plants,  if  this  remoleculization  is 
of  such  a  nature  that  the  results  are  poisonous  to  the  host, 
disease  follows.  If,  on  the  other  hand,  the  results  of  this 
remoleculization  should  not  be  poisonous  to  the  host,  the  only 
harm  resulting  would  be  merely  from  the  great  crowd  of  the 
parasitic  forms. 

The  history  of  the  experiment  and  observation  upon  this 
subject,  leaves  no  reasonable  room  to  doubt  that  remoleculiza- 
tions  occur  which  are  entirely  harmless,  and  that  remoleculi- 
zations  occur  with  the  production  of  the  most  deadly  poisons. 
While  every  imaginable  grade  between  these  two  may  occur. 


SIXTH  LECTURE. 


WASTE  PRODUCTS,  CONSIDERED  WITH  REFER- 
ENCE TO  THE  GERM  THEORY  OF  DISEASE. 

In  the  beginning  of  the  germ  theory  controversy,  Schwan 
seems  to  have  recognized  that  carbonic  acid  and  alcohol  were 
the  excrementitous  products  of  the  yeast  plant  (Annalen  der 
Pharmacie,  Band.  29,  S.  93  und  100).  Liebig,  in  opposing 
this  theory,  alludes  to  this  and  recognizes  that  this  conclusion 
would  necessarily  follow,  if  fermentation  were  proven  to  be 
the  result  of  life  force.  (Agricultural  Chemistry,  page  124.) 
Since  this  time,  however,  this  idea  seems  to  have  been  lost 
sight  of  by  writers  on  this  subject.  Sometimes  we  see  inde- 
finite allusions  to  it;  but  there  is  no  definite  expression  of 
the  general  law,  that  all  forms  of  life  must  have  their  specific 
waste  products,  as  they  are  seen  in  the  animal  forms.  The 
remoleculization  of  matter  is  continuous  with  the  duration  of 
life.  The  life  force  is  dependent  upon  the  remoleculization 
of  matter  for  its  support.  No  manifestation  of  the  life  force, 
in  any  form  whatever,  can  be  conceived  of  without  this  accom- 
paniment. As  the  steam  engine  is  dependent  upon  fire  for  its 
power,  so  is  the  life  force  dependent  upon  molecular  changes  in 
matter  for  its  continuous  existence.  As  steam  is  dependent  upon 
heat  for  its  generation,  and  the  expansive  force  by  which  the 
engine  is  driven,  so  is  matter  dependent  upon  the  life  force 
for  the  changes  of  molecular  form  through  which  that  life  is 
cognizable  to  our  senses.  We  can  have  no  conception  of  life 
in  the  material  form  without  the  accompaniment  of  these 
changes.  Any  other  form  of  life  than  this  must  be  that  spiritual 
condition  which  is  not  recognizable  by  our  physical  senses. 

Ill 


112  THE   GERM   THEORY   OF   DISEASE. 

All  forms  of  life  are  continually  taking  into  themselves 
fresh  increment  of  matter  in  some  form.  This  fresh  incre- 
ment of  matter  is  converted  into  other  forms,  for  the  support 
of  the  energies  of  that  life  which  performed  this  conversion; 
and  when  this  is  accomplished,  it  must  give  way  to  fresh  in- 
crements of  matter,  which  undergo  similar  remoleculizations. 
The  old  must  give  place  to  the  new.  There  is  no  such  thing 
as  standing  still,  except  with  certain  definite  provisions  for 
temporary  inactivity.  Otherwise  than  this,  inactivity  is 
death.  As  new  material  is  added,  the  old  must  be  disposed 
of,  must  be  cast  out,  or  built  up  into  formed  material,  where 
it  takes  no  further  part  in  the  physiological  activities  of  the 
organism.  Continuous  molecular  change  of  matter  is  the 
law  of  physiological  existence.  In  other  words,  the  remolecu- 
lization  of  matter  is  necessary  to  the  support  of  life  ;  and 
when  this  remoleculization  ceases  to  be  performed  by  the  life 
force,  except  under  the  provisions  of  rest,  that  life  ceases  to 
exist. 

As  the  living  form  must  be  supported  by  fresh  increment, 
so  it  must  give  back  excrement.  Life  is  not  to  be  supported 
by  the  continuous  remoleculization  of  the  same  matter.  After 
it  has  once  accomplished  its  function  in  the  economy,  it  be- 
comes unfitted  for  further  physiological  use,  and  is  disposed 
of  in  one  of  two  ways.  It  is  either  built  into  fixed  material, 
or  it  is  cast  out  as  excrement.  In  either  case  it  is  disassociated 
with  the  physiological  activity  of  the  organism.  The  sum  of 
the  excrement,  fixed  and  formed  material,  must,  in  all  cases, 
equal  the  sum  of  the  increment.  There  is  nothing  lost,  nothing 
gained.  All  increment  not  present  in  the  organism,  must 
have  been  given  back  to  the  outside  world  as  excrement,  no 
matter  what  the  form  of  life. 

There  is  a  general  law  to  be  observed  in  the  formation  of 
excrementitious  matters.  Liebig,  while  opposing  the  life- 


WASTE   PKODUCTS.  113 

theory  of  the  fermentations,  gives  expression  to  this,  as  a  law 
of  all  fermentation.  (I  translate  from  Chemische  Briefe,  6te 
Auflage  S.,  258.  "  Die  Gahrung  ist  stets  in  ihrem  Resultate 
eine  Spaltung  eineszusammen-gesetzten  Atoms  in  eine  sauers- 
tofFreiche  und  eine  sauerstoffarme  Verbindung;  indem  sich  in 
der  Alkohol-garung  eine  gewisse  Quantitat  von  sauerstoff 
von  den  elementen  des  zuckers  in  der  form  von  Kohlensaure 
trent,  erhalten  wir  den  brennbaren,  leicht  entziindlich  sauers- 
toffarmen  Alkohol.")  "  Fermentation  is  always,  in  its  results, 
a  splitting  of  combined  atoms  into  a  compound  rich  in 
oxygen,  and  a  compound  poor  in  oxygen  ;  so  in  alcoholic  fer- 
mentation, a  certain  amount  of  oxygen  is  divided  from  the 
sugar  in  the  form  of  carbonic  acid,  and  we  obtain  the  inflam- 
mable alcohol,  poor  in  oxygen." 

When  we  compare  this  statement  with  what  is  now  known 
of  fermentation  we  find  it  correct.  But  we  may  do  more  than 
this,  for  if  we  extend  it  so  as  to  cover  all  life,  in  whatever 
form,  we  find  that  it  is  still  correct ;  and  that  it  is  a  law  of 
the  formation  of  waste  products.  For  in  the  animal  forms 
we  find  as  excrementitious  products  the  same  carbonic  acid 
rich  in  oxygen,  and  urea  poor  in  oxygen.  In  the  higher 
plants  we  still  find  the  same  carbonic  acid  rich  in  oxygen, 
and  the  alkaloids  and  organic  acids  poor  in  oxygen.  Here 
we  see  as  the  final  result  of  the  remoleculizations  by  the  life 
force,  waste  products  analogous  to  those  of  the  yeast  plant. 
In  other  words  we  find  in  all  forms  of  life  a  respiratory 
waste  product  rich  in  oxygen,  and  an  urinary  waste  product 
poor  in  oxygen. 

I  have  already  shown  that  in  the  physiological  sense,  there 
is  a  close  resemblance,  a  certain  oneness  of  plan  existing 
among  all  forms  of  life  in  the  matter  of  taking  food.  Now 
it  is  my  purpose  to  show  that  this  identity  of  plan  is  extended 
to  all  the  living  forms  in  the  matter  of  waste  products  as  well. 


114  THE   GERM   THEORY   OF   DISEASE. 

While  there  are  almost  unending  differences  of  outward  con- 
formation there  is  a  continuous  physiological  sameness  in  them 
all.  While  certain  cells  are  endowed  with  the  power  of  com- 
bination for  building  wonderful  forms,  as  in  man  or  in  the 
tiger,  in  the  lofty  palm  or  the  forest  oak,  others,  not  pos- 
sessing the  power  of  organization  into  complex  forms,  fall 
apart  and  carry  on  their  physiological  processes  singly,  as  iii 
the  yeast  plant,  or  the  mycoderma  aceti.  In  the  unicellular 
organisms,  all  the  vital  functions,  so  far  as  they  are  differenti- 
ated, are  carried  on  in  the  single  cell ;  and  in  the  higher 
animals  which  proceed  from  the  growth  and  development  of 
some  single,  and  equally  minute  germ,  specialization  of  func- 
tion goes  hand  in  hand  with  specialization  of  physical  form. 
Yet  in  all  this  specialization  there  is  no  radical  change  in  the 
functions  of  the  individual  cells;  nor  is  the  sum  total  of  the 
physiological  phenomena  modified  in  their  nature.  In  the 
one  matter  of  seeds,  we  are  amazed  and  confused,  by  the 
never  ending  varieties  of  form ;  but  in  the  examination  of 
the  physiology  of  seed  forms  and  the  awakening  of  the  germ 
into  active  life,  we  find  each  to  consist  of  a  germ  with  the 
accompaniment  of  a  store  of  formed  food  material  for  the 
nutrition  of  that  germ,  until  it  has  formed  the  organs  for  the 
gathering  of  its  own  food ;  and  the  physiological  means  of 
using  that  store  is  practically  the  same  in  them  all.  If  we 
examine  the  egg,  the  result  is  the  same.  Among  the  varieties 
of  form  there  is  but  one  plan. 

In  most  cases,  apparent  new  functions,  seen  as  we  ascend 
the  scale  of  life,  consist,  when  closely  examined,  of  vicarious 
cell  action.  Not  a  new  function,  but  a  particular  function 
performed  for  the  community  of  cells,  so  to  speak,  by  certain 
cells  specialized  for  that  purpose;  as  we  have  already  seen 
in  the  matter  of  digestion.  We  find  the  specialization  of 
muscular  fibre  for  the  performance  of  complex  motion  through 


WASTE   PRODUCTS.  115 

which  a  portion  of  the  cells  of  the  body  act  for  the  whole, 
but  it  is  not  a  new  function,  but,  a  function  that  has  become 
specialized ;  for  in  the  unicellular  forms  we  have  motion 
without  muscular  fibre. 

So  we  might  go  on  showing  that  the  so-called  specialized 
functions  are  more  highly  developed  attributes  that  are  to  be 
found  in  unicellular  life.  But  this  is  unnecessary. 

Waste  products  may  be  divided  into  two  classes :  the 
respiratory  and  the  urinary.  The  respiratory  product  is 
always  rich  in  oxygen,  while  the  urinary  product  is  always 
comparatively  poor  in  oxygen.  This  distinguishing  feature 
remains  constant  for  all  forms  of  life,  whether  animal,  vege- 
table, or  the  lower  forms,  that  are  so  doubtful  that  some  have 
thought  it  well  to  create  for  them  a  separate  department. 

The  waste  products  of  the  animal  forms  are  sufficiently 
well-known.  The  consideration  of  them  has  been  entered 
into  by  every  author  who  has  written  on  the  subject  of 
physiology;  and  is  therefore  unnecessary  here.  I  will, 
however,  call  attention  to  some  important  facts  that  will 
be  of  use  in  the  consideration  of  the  variations  observed 
in  the  waste  products  of  some  of  the  lower  forms  of  life. 
There  is,  perhaps,  no  part  of  the  animal  frame  that  is  abso- 
lutely constant  in  its  chemical  components.  All  are  subject 
to  variations  within  certain  limits  that  are  by  no  means  well 
defined.  So  it  is  with  the  waste  products.  While  they  are 
constant  in  their  general  characters,  they  are  subject  to  varia- 
tions with  changes  in  the  character  of  the  food  employed  by 
the  animal.  For  instance,  if  my  urine  is  acid  to-day,  I  may 
render  it  alkaline  to-morrow,  or  next  day,  by  eating  a  few 
oranges  or  lemons.  The  small  amount  of  the  alkaline  base, 
combined  with  the  acids  of  the  fruit,  is  sufficient  to  bring 
about  this  change,  while  the  acid  itself  is  destroyed  by  remo- 
leculization.  This  instance  is  doubly  instructive,  for  if  we 
6* 


116  THE   GERM    THEORY   OF   DISEASE. 

take  into  the  economy  a  simple  substance,  that  substance,  if  not 
thrown  out  of  physiological  activity,  by  being  built  into  fixed 
or  formed  material,  must  appear,  in  some  form,  in  the  waste 
products ;  and  in  this  instance  it  is  found  in  the  form  of  urate 
of  potassa  and  urate  of  soda ;  while  the  acid  with  which  it  was 
associated,  being  dependent  on  its  molecular  structure  for  its 
chemical  characters,  is  destroyed  by  remoleculization.  Its 
component  elements  appear,  but  in  other  molecular  forms. 
Hence,  the  effect  on  the  waste  product  is  not  different  from 
that  which  would  have  been  brought  about  if  the  alkaline 
base  alone  had  been  taken.  This  may  be  stated  as  a  general 
law  for  the  organic  acids  combined  with  the  alkaline  bases. 

All  of  the  excremeutitious  products  possess  toxic,  or  poison- 
ous properties  in  some  degree.  If,  by  the  occurrence  of  acci- 
dent or  disease,  urea  be  retained  in  the  blood  of  an  animal,  it 
soon  presents  symptoms  of  toxaemia,  and  if  the  accumulated 
urea  is  not  speedily  eliminated,  the  animal  dies.  This  is  a 
general  law  of  the  waste  products.  No  living  being  can  sus- 
tain life  with  a  large  percentage  of  its  waste  product  retained 
in  its  circulation.  Neither  can  a  micro-organism  continue  to 
grow  after  a  certain  amount  of  its  waste  products  have  accu- 
mulated in  the  menstruum  in  which  it  is  placed.  Urea  may 
be  regarded  as  the  alkaloid  of  the  animal  kingdom,  and  is  the 
analogue  of  the  alkaloids  of  the  vegetable  kingdom. 

WASTE  PRODUCTS  OF  PLANTS. 

The  consideration  of  the  waste  products  of  the  vegetable 
kingdom  is  especially  difficult,  for  several  reasons  :  Plants  are 
characterized  by  the  large  amount  of  their  formed  material, 
as  compared  with  the  food  material  consumed  by  them  in 
their  processes  of  vital  activity;  and  therefore,  the  amount  of 
their  waste  products  actually  excreted  is  proportionately  small. 
In  them,  however,  other  means  are  found  for  freeing  their 


WASTE    PRODUCTS   OF   PLANTS.  117 

circulating  fluids  of  waste  materials,  than  that  of  actual  ex- 
cretion as  seen  in  the  animal  forms,  which  will  be  considered 
farther  on.  There  is,  however,  a  sufficiently  copious  excretion 
of  the  respiratory  waste  product,  carbonic  acid,  in  plants,  and 
in  addition  to  this,  oxygen.  These  are  too  well  known  to 
require  further  comment  here. 

There  is,  also,  a  true  excretory  function  performed  by  the 
roots  of  plants,  and  by  the  seeds  in  the  process  of  germination. 
"When  barley,  or  other  grain,  is  caused  to  germinate  in  pure 
chalk,  acetate  of  lime  is  uniformly  found  to  be  mixed  with 

it,  after  the  germination  is  somewhat  advanced 

In  this  case  the  acetic  acid  must  have  been  given  off  (excreted) 
by  the  young  roots  during  the  process  of  the  germination  of 
the  seed."  (Vide  Johnston's  Agricultural  Chemistry, 
page  81.) 

This  well  authenticated  fact  may  be  regarded  as  the  foun- 
dation of  the  theory  that  plants  are  endowed  with  the  power 
of  excretion.  It  is  supported  by  the  authority  of  Decandolle, 
and  the  convincing  experiments  of  Macaire,  although  the  ex- 
periments of  others  have  shown  that  this  excretion  is  limited 
to  very  small  amounts  of  matter.  Macaire  seems  to  have 
found  opium  in  the  soil  in  which  the  poppy  plants  grew.  He 
also  found,  in  washing  the  soil  with  pure  water,  that  it  yielded 
a  considerable  quantity  of  acetic  acid  and  a  trace  of  a  brown 
organic  matter. 

Liebig  devotes  considerable  space  to  this,  in  his  agricultural 
chemistry,  with  especial  reference  to  the  possible  effects  of 
these  excrementitious  substances  on  the  rotation  of  crops. 
Other  chemists  have  also  occupied  themselves  with  it,  and 
while  it  has  been  definitely  shown  that  in  some  special  cases 
plants  may  eliminate  a  sufficient  quantity  of  excrementitious 
matter  to  prove  injurious  to  successive  generations  growing  in 
the  same  soil,  the  rule  is  that  poisoning  from  this  cause  is  not 


118  THE   GERM   THEORY   OF    DISEASE. 

to  be  expected.  In  many  instances,  however,  it  is  found  that 
individual  plants  are  poisonous  to  others  growing  in  their 
neighborhood.  It  is  rare  to  see  a  very  large  black  walnut 
tree  that  has  not  a  clearing  around  it,  wherever  it  may  stand 
in  the  forest.  This  is  not  on  account  of  its  shade,  but  some- 
thing eliminated  by  the  tree  that  is  hurtful  to  other  trees.  I 
remember  well  an  effort  to  raise  corn  on  the  south  side  of  a 
row  of  walnut  trees.  The  experiment  was  continued  for 
many  years.  The  corn  was  injured  seriously  for  many  feet 
distant,  where  it  was  never  shaded  by  the  trees.  Very  many 
such  instances  are  known.  Enough  has  been  demonstrated 
to  show  conclusively,  that  most  of  the  substances  formed  in 
the  fermentations  are  also  excreted  in  very  small  amounts,  by 
various  plants.  Even  alcohol  and  ammonia  are  formed  in 
this  way,  in  small  quantities.  Although  these  substances,  as 
a  rule,  contain  no  nitrogen,  their  chemical  construction  is  such 
as  to  show  their  relationship  to  urea,  and  leave  no  doubt  that 
they  are  properly  analogues  of  that  product  in  the  animal 
kingdom. 

ALKALOIDS. 

By  far  the  most  important  compounds  to  be  considered  in 
this  connection  are  the  alkaloids.  These  bear  the  same  rela- 
tion to  plants  that  urea  bears  to  the  animal  forms.  There  is 
seen  in  their  chemical  conformation  and  characteristic  prop- 
erties a  marked  relationship;  and  yet  among  them  is  found 
a  wide  divergence  of  poisonous  effects.  All  possess,  in  some 
degree,  the  power  of  intoxication,  while  a  few  are  the  most 
virulent  poisons  known.  Nearly  all  are  composed,  as  urea, 
of  carbon,  hydrogen,  nitrogen,  and  oxygen.  In  a  few  of 
them  oxygen  is  lacking;  and  in  all  the  nitrogen  is  in  smaller 
proportion  than  in  urea.  As  we  descend  the  scale,  the  nitro- 
gen disappears,  the  oxygen  is  increased,  and  we  have  the 
organic  acids  and  alcohols.  All  of  these  are,  properly,  waste 


ALKALOIDS.  119 

products  of  the  vegetable  kingdom,  though  they  are  not  all 
excreted. 

As  we  have  already  seen,  the  higher  plants  are  marked  by 
the  apparently  small  amount  of  their  waste  products  and  the 
large  amount  of  their  formed  material.  The  formed  material 
presents  two  very  marked  characteristics,  which  will,  perhaps 
be  better  understood  if  we  designate  them  as  formed  material 
and  "  fixed  "  material.  Then  we  may  class  the  formed  material 
as  that  which  is  elaborated  and  stored  away  for  future  use, 
such  as  the  starch,  oil,  etc.,  surrounding  the  germ  in  the 
seeds,  and  in  certain  organs  of  the  plant,  and  various  other 
products  designed  for  future  employment  by  the  vital  ener- 
gies of  the  organism.  The  "fixed"  material,  on  the  other 
hand,  is  such  as  is  placed  permanently  beyond  the  vital  ener- 
gies of  the  organism.  Some  portions  of  the  fixed  material 
may  still  be  of  use  to  the  plant  by  the  physical  support  it 
gives  to  its  organs;  as  lignin,  which  forms  the  stems  and 
branches  of  trees,  and  the  bark,  which  serves  them  as  a  pro- 
tection. They  are  not,  however,  of  any  further  physiological 
use  to  the  plant  after  having  once,  or  a  few  times,  served  as 
conduits  for  the  circulating  fluids. 

Although  waste  products  may  be  found  in  the  fluids  of  the 
plant,  as  in  the  blood  of  the  animal,  it  is  in  this  fixed  material 
that  we  find  the  bulk  of  these  substances;  and  it  is  here  that 
the  toxic  principles  are  found  in  greatest  abundance.  Instead 
of  being  excreted,  thrown  out  to  the  outer  world,  they  are 
stored  in  the  disused  cells  of  the  wood  and  bark,  united  with 
other  waste  products  in  the  form  of  insoluble  compounds. 
This  fact  seems  to  have  prevented  an  early  recognition  of 
their  real  nature. 

Sachs,  in  his  text-book  of  botany,  describes  them  as  "  de- 
gradation products,  which  are  no  longer  useful  to  the  plant/' 
and  as  "  secondary  products  of  metastasis."  When  we  look 


120  THE   GERM   THEORY    OF   DISEASE. 

over  the  products  thus  set  apart  by  Sachs,  we  find  that  nearly 
all  of  them  may  be  set  down  at  once  as  analogues  of  the  urine 
in  the  animals,  of  the  alcohol,  the  acetic  acid,  the  butyric  acid, 
etc.,  of  the  fermentations. 

It  is  to  these  products  that  we  look  for  the  most  of  the 
vegetable  substances  now  employed  as  medicines.  The  active 
principles  of  these  are  the  alkaloids.  Therefore  their  effect 
upon  the  animal  economy  is  well  known  to  medical  students, 
and  need  not  be  recited  here.  There  are  many  other  sub- 
stances found  in  the  same  relationship  to  the  vital  energies  of 
the  plant,  which  are  worthy  of  special  consideration,  if  we  had 
the  time  at  our  disposal.  Tannic  acid  is  one  of  the  most  constant 
of  these  products,  and  there  are  a  large  number  of  others  not 
yet  mentioned.  We  will  only  mention  one  other  class  of 
substances,  the  coloring  matters  which  remain  in  the  wood 
cells  in  a  fixed  condition,  as  a  result  of  secondary  metastasis. 
Precisely  similar  phenomena  are  seen  in  the  Micrococcus 
Chromogenes,  of  which  there  are  several  varieties  known. 
All  such  circumstances  serve  to  point  us  forward  in  our  efforts 
to  explain  the  mysteries  of  nature. 

BACTERIA. 

When  we  come  to  consider  the  bacteria,  and  the  allied 
forms  of  life,  we  are  at  once  amazed  and  astounded  at  the 
wonderful  power  they  possess  in  the  remolecullzation  of  matter. 
This  is  one  of  their  especial  characteristics.  This  seems  to  be 
the  form  of  life  in  which  the  largest  amount  of  food  material 
is  consumed,  and  the  largest  amount  of  waste  products  given 
back,  with  the  least  building  of  tissue.  The  largest  amount 
of  remoleculization  with  the  least  amount  of  formed  or  fixed 
material.  A  whole  jar  of  milk  is  turned  sour,  every  particle 
of  its  sugar  of  milk  converted  into  lactic  acid,  and  yet  the 
amount  of  the  formed  material  is  so  insignificant  that  it  re- 


BACTERIA.  121 

quires  an  acute  and  trained  observer,  provided  with  the  best 
means  of  search,  to  find  a  trace  of  it.  When  a  small  amount 
of  yeast  is  added  to  a  solution  of  sugar,  the  whole  of  the 
sugar  will  be  remoleculized,  producing  carbonic  acid  and 
alcohol  within  a  few  hours,  with,  apparently,  no  increase  of 
the  yeast.  In  this  instance,  however,  the  yeast  has  grown,  and 
performed  its  function  of  remoleculization,  under  the  most 
difficult  circumstances,  for  the  reason  that  it  is  deprived  of 
the  nitrogen  necessary  for  the  building  up  of  its  cellulose 
and  albumen.  Under  these  circumstances  the  amount  of  yeast 
may  actually  decrease,  as  was  shown  by  Liebig  many  years 
ago.  Pasteur  seems  to  have  proven  that  in  this  case  the 
young  yeast  cells  grow  at  the  expense  of  the  nitrogen  in  the 
old  cells,  and  thus  destroy  them  to  such  an  extent  that  the 
whole  quantity  of  the  yeast  is  diminished,  and  the  vital 
energies  of  the  plant  weakened.  This  example  serves  to 
show  the  wonderful  power  of  these  low  organisms. 

Then  we  may  take  the  example  of  the  destruction  of  the 
dead  carcass.  The  history  of  the  experimentation  of  the  past 
shows  conclusively  that  it  does  not  decompose,  if  protected 
from  these  low  organisms.  Yet  within  a  few  days  it  is 
swarming  with  this  form  of  life,  in  the  presence  of  which  it 
melts  away  like  ice  before  a  summer  sun.  It  is  first  attacked 
by  one  form,  which  consumes  and  throws  out  its  waste  pro- 
ducts as  long  as  it  can  grow  in  the  continually  increasing 
quantity  of  its  own  excreta.  Then  it  must  give  way  to  others 
that  have  already  appeared  on  the  scene  of  action,  to  which 
the  waste  products  of  the  first  are  no  hindrance.  These,  in 
turn,  very  soon  give  way  to  still  other  forms,  which  again 
remoleculize  the  waste  products  of  all  the  former  that  may 
retain  a  semi-solid  or  a  liquid  form,  with  any  residue  of  the 
original  carcass  that  may  still  remain;  and  in  an  almost 
incredibly  short  time  the  whole  carcass  has  disappeared.  The 


1  22  THE   GERM   THEORY   OF   DISEASE. 

labors  of  Pasteur  have  thrown  much  light  upon  this  subject. 
The  fact  that  the  acetic  acid  plant  will  again  remoleculize  the 
waste  product  of  the  vinous  yeast  plant,  alcohol,  and  after 
that  the  mucidines  will  still  remoleculize  the  acetic  acid,  con- 
verting it,  in  turn,  into  other  compounds,  is  full  of  instruction 
for  all  these  processes.  Why  is  it  that  the  yeast  plant  cannot 
grow  continuously  in  the  same  menstruum,  if  proper  food 
material  be  furnished  it?  It  is  a  well  known  fact  that  only 
a  certain  percentage  of  alcohol  can  be  formed  in  this  way, 
and  that  to  obtain  a  greater  percentage  we  must  resort  to 
distillation.  The  plant  is  choked  by  its  own  excreta,  alcohol. 
If  this  could  be  eliminated  the  growth  of  the  plant  could  be 
continued. 

An  example  of  this  is  found  in  the  bacterium  lactis.  If 
lime  is  added  to  the  solution,  lactate  of  lime  is  formed  and 
the  excretory  product  of  the  plant,  lactic  acid,  is  artificially 
eliminated,  and  the  plant  is  found  to  grow  continuously  in 
the  same  menstruum,  as  long  as  supplied  with  food  material, 
and  lime  to  fix  or  eliminate  its  excreta.  The  form  of  excre- 
tion employed  by  the  higher  plants  is  artificially  produced. 
This  law  of  the  relation  of  excretory  products  to  the  life  that 
formed  them  is  universal.  It  applies  with  the  same  force  to 
the  micro-organisms  that  it  does  to  the  higher  animals,  or  to 
man  himself. 

It  would  seem  that  the  vegetable  world  is  divided  into  two 
great  classes  of  life  forms,  and  that  ifc  is  the  office  of  the  one 
to  build  up,  and  the  office  of  the  other  to  tear  down.  Of  all 
the  life  forms,  the  higher  plants  have  the  greatest  power  of 
structure  building,  both  as  regards  quantity,  in  comparison 
with  the  amount  of  the  material  consumed,  and  as  to  the 
actual  quantity  of  structure  formed ;  while,  in  the  lower 
plants,  the  bacteria  and  their  allied  forms,  exactly  the  opposite 
of  this  is  found,  in  every  particular.  No  other  form  of  life 


BACTERIA.  123 

consumes  so  much  in  comparison  to  the  amount  of  structure 
built.  They  are  emphatically  the  destroyers  of  organic  forms; 
physiologically  constructed  to  and  for  this  end.  Yet,  they 
must  digest  their  food ;  if  it  be  solid,  or  semi-solid,  it  must 
be  liquefied,  in  order  to  be  absorbed.  Then  it  must  enter 
into  the  cells  by  the  process  of  osmosis,  and  under  the  influ- 
ence of  the  life  force  be  converted  into  protoplasm — albu- 
minoids— into  the  tissue  of  the  growing  plant. 

After  this  come  the  waste  products.  How?  The  cell 
dies?  No.  This  will  not  explain  the  phenomenon.  If  it 
were  the  death  of  the  cells,  we  would  find  the  chemical  forms 
of  the  cells  in  the  waste  products.  This  is  not  the  case. 
Death  does  not  alter  the  chemical  forms.  Therefore,  there  is 
another  remoleculization  for  the  formation  of  the  waste  pro- 
ducts ;  a  vital  process  of  shedding  out  the  used  material  in 
two  general  forms.  The  life  force  letting  go  of  the  matter  it 
has  had  in  its  grasp,  and  casting  it  out  as  no  longer  of  use  to 
it.  The  formation  of  waste  products  is  not,  in  any  true  sense, 
a  process  of  dying. 

Life  resides  in  matter  which  it  has  formed  into  such  molec- 
ular groupings  as  will  suit  its  purposes,  but  matter  does  not 
live.  Electricity  may  be  resident  for  a  time  in  the  Leyden 
jar,  but  such  a  jar  is  not  electricity.  It  may  be  said  to  be 
electrified,  and  matter  may  be  said  to  be  vivified.  If  life 
discharges  matter  which  it  has  had  in  its  grasp,  the  act  is  a 
vital  one,  and  as  all  changes  in  matter  under  the  influence  of 
the  life  force  consist  in  remoleculization,  so  does  this;  hence, 
waste  products  are  always  in  different  molecular  forms  from 
the  tissues  from  which  they  are  cast  off,  though  they  consist 
of  the  same  elements.  It  is  by  a  vital  process,  then,  that  the 
waste  products  are  separated  from  the  living  organism,  and  in 
the  bacteria  the  general  laws  of  physiology  remain  unchanged. 
Here,  as  elsewhere,  we  find  the  definite  respiratory  product, 


124  THE   GERM   THEORY   OF   DISEASE. 

and  the  toxic  or  urinary  product.  A  sufficient  number  of 
these  have  now  been  studied  for  us  to  gain  some  notion  of 
them;  yet  our  knowledge  is  still  limited  to  a  few  forms 
among  the  bacteria  and  their  allies.  The  best  known  is  the 
yeast  plant.  In  this  we  have  alcohol,  succinic  acid  and  glyce- 
rine, as  the  urinary  excrement.  The  bacterium  lactis  produces 
lactic  acid ;  the  mycoderma  aceti  produces  acetic  acid.  These 
names  properly  represent  so  many  families,  each  of  which 
contains  a  number  of  varieties.  Saccharine  substances  form 
suitable  food  for  them  all.  Two  of  them  will,  however,  grow 
equally  well  in  substances  not  saccharine.  Another  form 
produces  butyric  acid;  another,  a  kind  of  mucus;  another, 
ammonia;  while  others  still,  produce  as  their  waste  products, 
all  of  the  ill-smelling  products  of  putrefaction.  I  append  a 
table  of  those  best  known,  in  connection  with  a  table  of  the 
waste  products  of  other  forms  of  life,  for  comparison. 

TABULATED  STATEMENT  OF  THE  WASTE 
PRODUCTS  OF  VARIOUS  ORGANISMS. 

RESPIRATORY   PRODUCTS.  TOXIC    PRODUCTS. 

ANIMALS. 

Carbonic  Acid....... C02      Urea CH4N20 

Creatine C4H9N302 

Creatinine C4H7N30 

Uric  Acid C5H4N403 

Hippuric  Acid C9H9N,  03 

PLANTS. 

Carbonic  Acid C02      Theine C8H10N402 

Oxygen 0      Veratrine C32H52N208 

Morphine C17H19N03 

Quinine C20H24N202 

Strychnine C21H22N202 

Atropine C^HgsNOg 

Piperine C1VH19N03 


WASTE   PRODUCTS   OF   VARIOUS   ORGANISMS.  125 

RESPIRATORY   PRODUCTS.  TOXIC    PRODUCTS. 

Carbonic  Acid C02    Nicotine C10H14N2 

Oxygen 0    Coniine C8H15N 

Curarine C10H15N 

Tannic  Acid C14H1009 

Acetic  Acid C2H402 

Citric  Acid C6H8Or 

Malic  Acid C4H605 

Oxalic  Acid C2H204 

BACTERIA. 
Alcoholic  Fermentation. 

Carbonic  Acid C02      Alcohol C2H6O 

Succinic  Acid C4H604 

Glycerine C  H803 

Acetic  Fermentation. 
Carbonic  Acid C02      Acetic  Acid C2H402 

Lactic  Fermentation. 
Carbonic  Acid C02      Lactic  Acid C3H603 

Viscous  Fermentation. 

Carbonic  Acid C02      Mannite C6H1406 

Gum C12H20010 

Tartaric  Fermentation. 

Carbonic  Acid C02      Propionic  Acid C3H602 

Hydrogen H 

Butyric  Fermentation, 

Carbonic  Acid  C02      Butyric  Acid C4H803 

Hydrogen H 

Ammoniacal  Fermentation. 
Carbonic  Acid  C02      Ammonia NH3 

(These  two  products  unite  to  form  ammonia  carbonate.) 

Putrefactive  Fermentation. 

Carbonic  Acid C02      Valerianic  Acid C5H1002 

(Complex.)  Ammonia NH3 

Sulphydric  Acid HS 

Fat  Acids  (various  eqv.) C  H  0 


126  THE   GERM    THEORY    OF   DISEASE. 

ALKALOIDS. 

There  is,  perhaps,  no  other  one  set  of  organic  compounds 
that  have  puzzled  chemists  more  than  those  given  in  this 
table,  or  that  have  been  and  still  continue  to  be  of  more  in- 
terest to  the  scientific  world.  The  table,  as  it  stands,  is  only 
intended  to  give  an  outline  view  of  these  organic  matters  as  a 
class,  by  setting  before  you  fairly  chosen  specimens  from  the 
different  forms  of  life.  It  is  not  intended  to  be  in  any  wise 
exhaustive,  but  simply  a  comparison  of  these  products.  The 
similarity  of  their  chemical  construction  will  be  apparent  at  a 
glance,  and  yet  they  differ  greatly  in  their  toxic  properties. 
Some,  as  strychnine,  are  violent  poisons  to  the  animal  king- 
dom. While  others,  as  some  of  the  acids,  are  mild  irritants. 
Most  of  those  from  the  vegetable  world  are  useful  as  medi- 
cines, while  many  are  highly  prized  as  condiments.  The 
members  of  the  acid  series  vary  from  the  alkaloids  in  that 
they  contain  no  nitrogen,  and  they  also  vary  as  markedly  in 
their  toxic  properties.  Their  close  similarity  to  the  alcohols 
will  be  noticed.  It  will  also  be  noticed  that  some  of  the 
waste  products  of  higher  plants  are  the  same  as  those  of  lower 
organisms.  This,  perhaps,  would  not  be  expected  at  first 
glance;  yet  when  we  come  to  consider  that  all  are  plants,  we 
should  expect  a  similarity.  There  is,  perhaps,  an  important 
difference  to  be  observed  here.  The  alkaloids  of  the  higher 
plants,  from  the  nature  of  their  mode  of  excretion,  are  thrown 
out  of  physiological  activity,  by  being  combined  with  the  veg- 
etable acids,  mostly  in  the  form  of  insoluble  salts,  and  thus 
laid  away  in  the  "  fixed  material "  of  the  plant.  On  the  other 
hand,  the  animal  alkaloids,  urea,  uric  acid,  etc.,  are  eliminated 
in  a  soluble  condition.  In  case  of  the  micro-organisms,  the 
waste  products  are  very  generally  eliminated  in  a  soluble 
condition  also.  There  seem  to  be  some  exceptions  to  this 


ALKALOIDS.  127 

rule,  as  in  the  chromogenes.     To  what  extent  this  may  occur, 
does  not  yet  appear. 

But  the  comparatively  more  abundant  waste  product  of  the 
lower  forms  is  of  much  importance  in  this  connection.  Those 
given  are  from  the  few  that  have  been  best  studied.  In  these 
no  proper  alkaloids  have,  as  yet,  been  made  out  by  isolation 
and  exact  analysis,  but  we  cannot  argue,  from  this  circum- 
stance, that  none  of  the  lower  organisms  produce  true  alka- 
loids. As  yet,  but  very  few  of  them  have  been  accurately 
studied,  and  these,  for  the  most  part,  have  been  those  that 
have  been  found  useful  rather  than  poisonous.  Some  exami- 
nations already  made  show  a  very  near  approach  to  the  deter- 
mination of  the  nature  of  some  of  these  poisonous  substances; 
and  although  no  sufficient  chemical  analysis  has  yet  been 
made,  the  action  of  the  substances  upon  the  animal  economy, 
so  far  as  trial  has  been  had,  go  to  show  the  similarity  of  these 
poisons  to  the  alkaloids  from  the  higher  plants.  This  has 
been  remarked  by  many  experimenters,  as  I  shall  show  pre- 
sently. Therefore,  we  have  much  reason  to  believe  that  true 
alkaloids,  of  a  poisonous  nature,  will  be  isolated  at  no  distant 
day.  We  have  already  abundant  evidence  that  poisonous 
properties  are  developed  by  a  number  of  these  forms.  Other- 
wise, how  can  we  account  for  the  results  of  the  Bacillus  An- 
thracis?  How  else  can  we  account  for  sepsis,  on  the  germ 
theory,  except  to  suppose  that  a  poisonous  alkaloid  is  one  of 
the  products  of  the  organism  ?  How  else  can  we  explain  Dr. 
Koch's  results  in  the  production  of  gangrene  in  mice,  but  to 
suppose  that  some  product  of  the  remoleculizations  by  the 
organisms  spread  among  the  tissues  of  the  animals  and  de- 
stroyed them  wherever  they  went.  He  found  that  after  they 
had  once  made  a  beginning,  the  tissues  were  always  destroyed 
in  advance  of  the  growing  organisms,  without  contact.  This 
strongly  illustrates  the  idea  of  the  formation  of  a  poison 


128  THE   GERM   THEORY   OF   DISEASE. 

which  is  thrown  out  from  the  organism.  Again,  in  the  matter 
of  sepsis,  already  referred  to,  it  has  been  abundantly  shown 
that  the  fluids  contaminated  by  the  micrococci  are  poisonous, 
when  separated  from  the  organisms;  thus  proving,  again,  that 
there  is  an  organic  poison  developed,  which  is  fully  capable  of 
producing  its  effects  in  the  absence  of  the  life  that  produced 
it,  the  same  as  is  seen  in  the  alkaloids  from  the  higher  plants. 
This  has  taken  the  name  of  sepsin,  after  the  order  of  the 
naming  of  the  vegetable  poisons ;  although  it  has  not,  as  yet, 
been  properly  isolated  and  examined. 


SEVENTH  LECTURE. 


POISONS. 

In  this  lecture  I  propose  to  examine  more  particularly  the 
evidence  given  by  experimenters  of  the  finding  of  the  poison- 
ous products  of  micro-organisms. 

Koch,  after  injecting  putrid  blood  into  mice  and  noting 
that  a  large  amount  killed  by  direct  poisoning,  while  a  very 
small  amount  produced  disease,  says  of  the  first :  "  No  inflam- 
mation can  be  observed  in  the  neighborhood  of  the  place  of 
injection.  The  internal  organs  are  also  unaltered.  If  the 
blood  taken  from  the  right  auricle  be  introduced  into  another 
mouse,  no  effect  is  produced.  Bacteria  cannot  be  found  in 
any  of  the  internal  organs,  nor  in  the  blood  of  the  heart.  An 
infectious  disease  has  not  been  induced  as  the  result  of  the 
injection.  On  the  other  hand,  there  can  be  no  doubt  that 
the  death  ef  the  animal  was  due  to  the  soluble  poison,  sepsin, 
which  has  been  shown  by  the  researches  of  Bergman,  Panum, 
and  various  other  investigators,  to  exist  in  putrid  blood.  The 
animal  has  accordingly  died,  not  from  an  infectious  disease, 
but  from  a  chemical  poison.  This  supposition  is  confirmed 
by  the  fact  that  when  less  fluid  is  introduced  into  the  animal 
the  symptoms  of  poisoning  are  less  marked,  and  are  quite 
absent  when  one,  or  at  most,  two  drops  are  injected.  After 
the  use  of  such  a  small  quantity  of  blood,  mice  often  remain 
permanently  without  any  morbid  symptoms.  But  a  third  of 
them  will  become  ill  after  the  lapse  of  about  twenty-four 
hours,  during  which  time  they  have  remained  perfectly 
healthy.  The  symptoms  which  are  then  present  are  charac- 

129 


130  THE   GERM    THEORY    OF    DISEASE. 

teristic  and  constant,  and  are  in  no  case  preceded  by  any  of 
the  symptoms  of  poisoning  previously  described." 

These  experiments  show  very  distinctly  that  the  experi- 
menter was  dealing  with  a  diffusible  poison  of  virulent 
character,  produced  by  the  organisms,  but  acting  without 
them,  as  the  alkaloids  from  the  higher  plants  would  act. 

Dr.  Sternberg  says  (page  257):  "  It  is  not  alone  by  invad- 
ing the  blood  or  tissues  that  bacteria  exhibit  pathogenic 
powers.  Chemical  products  evolved  during  their  vital  activ- 
ity, external  to  the  body,  or  in  abscesses  and  in  suppurating 
wounds,  or  in  the  alimentary  canal,  may  doubtless  be  absorbed, 
and  exercise  an  injurious  effect  upon  the  animal  economy. 
Indeed,  we  have  experimental  evidence  that  most  potent 
poisons  are  produced  during  the  putrefactive  decomposition  of 
organic  matter.  The  poisons  resembling  the  vegetable  alka- 
loids in  their  reactions^  called  ptomains  by  Selmi,  who  first 
obtained  them  from  the  cadaver,  are  fatal  to  animals  in 
extremely  minute  doses." 

Klebs  said,  at  the  International  Medical  Congress  at 
London,  that  the  effects  of  micro-organisms  were  probably 
due  to  fine  chemical  workings.  Very  many  of  the  experi- 
menters in  this  field  have  spoken  in  a,  like  manner  of  their 
findings,  all  of  which  go  to  show  that  the  worker  in  this  line 
of  research  soon  comes  to  feel  that  he  is  dealing  with  a  poison 
evolved  by  the  organisms  he  has  under  observation. 

Gradle  says  (page  66):  "The  successive  chemical  stages  of 
the  putrefactive  change  have  as  yet  been  incompletely  traced. 
The  changes  which  albumen  undergoes  resemble  at  first  the 
process  of  digestion.  It  is  converted  into  soluble  forms, 
partly  peptone,  and  then  split  up  into  leucin  and  tyrosin.  Sub- 
sequently numerous  volatile  fatty  acids,  and  various  poly- 
atomic alcohols  (phenol,  skatol,  indol),  appear,  as  well  as  a 
host  of  other  substances  in  traces.  Amongst  them  are  a  variety 


POISONS.  131 

of  poisonous  agents,  especially  some  alkaloids  (ptomains)." 
The  most  constant  bacterial  form  met  with  in  putrefaction  is 
the  bacterium  termo.  Some  attempts  have  been  made  to  iso- 
late and  examine  septic  poisons.  This,  so  far,  has  only  served 
to  show  more  positively  the  production  of  poisons  and  the 
nature  of  their  action.  Panum  found  the  poison  formed  in 
the  decomposition  of  nitrogenous  substances  was  reduced  in 
virulence  about  one-fifth  by  eleven  hours  continuous  boiling 
of  the  infusion.  This  continuous  boiling  was  certainly  suffi- 
cient to  show  that  the  poisonous  effects  were  not  due  to  living 
micro-organisms  remaining  in  the  fluid.  In  this  case,  more- 
over, some  flakes  of  coagulated  albumen  were  found  in  the 
liquid,  which  upon  trial  proved  to  contain  a  very  virulent 
poison.  This  fully  Accounts  for  the  loss  of  virulence  by  the 
liquid.  This  experimentation  shows  that  the  substance  had 
none  of  the  characters  of  a  molecular  motion  poison  described 
by  Baron  Liebig;  nor  is  it  a  decomposing  substance  or  a 
ferment,  as  each  and  all  of  these  are  destroyed  by  heat.  The 
chemical  structure  of  the  substance  is  of  a  more  stable  nature. 
There  is  a  sharp  distinction  manifest  between  the  action  of 
these  poisons  when  developed  in  the  animal  body  by  the  re- 
moleculization  of  the  organisms  in  situ,  and  when  developed 
out  of  the' body,  collected  and  administered  separate  from  the 
organisms.  In  the  latter  case,  the  effects  produced  are  similar 
in  their  general  character  to  that  of  the  alkaloids  from  the 
higher  plants,  that  is,  comparatively  speaking,  they  are  im- 
mediate. The  disturbance  is  usually  manifest  within  a  few 
hours  at  most;  and  if  the  animal  withstands  this  immediate 
effect  of  the  poison  it  returns  to  health,  i.  e.,  all  the  symptoms 
pass  away  and  no  disease  is  produced ;  whereas,  if  the  micro- 
organisms which  elaborate  the  poison  are  planted  in  the 
tissues  of  the  animal  and  grow,  there  is  no  such  immediate 
poisoning.  On  the  contrary,  it  remains  well  for  a  day  or 
7 


132  THE   GEKM   THEORY   OF   DISEASE. 

more,  and  then  the  symptoms  come  on  more  slowly  and  grad- 
ually increase  in  violence  usually  until  death  is  induced.  A 
progressive  disease  is  the  result  in  the  one  case,  an  immediate, 
but  transient  poisoning  in  the  other.  This  difference  in  the 
results  of  inoculations  made  with  fluids  rendered  poisonous  by 
the  development  of  micro-organisms  within  them,  and  similar 
inoculations  with  fluids  containing  micro-organisms  but  with- 
out sufficient  developed  poison  to  produce  immediate  effects, 
has  been  marked  by  a  large  number  of  investigators  and  is 
now  perfectly  well  known. 

Putrefaction  does  not  always  result  in  the  formation  of 
virulent  poisons.  Many  times  meats,  or  meat  infusions,  may 
rot  away,  and  poisons  of  a  very  marked  character  cannot  be 
found  at  any  stage  of  the  process.  This  difference  must  be 
explained  by  the  fact  that  the  same  micro-organisms  have  not 
grown  in  the  one  as  in  the  other.  If  the  ordinary  bacteria  of 
decomposition  are  accompanied  by  a  form  that  produces  a 
virulent  alkaloid  as  a  result  of  its  remoleculizations,  the  poison 
will  be  found,  otherwise,  it  will  not.  Just  as  in  a  mass  of 
plants,  one,  or  a  few  only  of  the  many,  will  produce  a  viru- 
lent poison,  though  all  grow  in  the  same  soil.  Again,  as  we 
have  said,  the  mycoderma  aceti  will  feed  upon  the  alcohol 
formed  as  the  waste  product  of  the  vinous  yeast  plant.  In 
the  same  way  other  micro-organisms  may  feed  upon  and 
destroy,  through  their  remoleculizations,  the  poisonous  pro- 
ducts of  those  that  may  have  gone  before  them.  Hence,  it  is 
found  that  septic  cadavers  are  apt  to  lose  their  septic  characters 
as  decomposition  advances.  These  facts,  while  they  serve  to 
illustrate  the  manner  of  the  formation  of  poisons,  also  illus- 
trate the  extreme  complexity  of  the  subject. 


FARTHER   INVESTIGATION   NEEDED.  133 

FARTHER  INVESTIGATION  NEEDED. 

Many  other  instances  of  a  like  nature  might  be  brought 
forward,  if  time  would  permit,  but  it  is  no  part  of  my  inten- 
tion to  treat  this  subject  exhaustively.  Some  of  the  cases 
seem  to  show  that  the  poison  is  of  the  nature  of  a  local  irri- 
tant only,  as  appears  in  Dr.  Koch's  demonstration  of  the 
bacillus  tuberculosis ;  while  many  others  seem  to  be  general 
poisons,  with  special  tendencies  to  particular  organs,  as  is  seen 
in  the  splenic  fever  produced  by  the  bacillus  anthracis.  This 
is  sufficient  to  show  that  there  is  much  yet  to  be  learned  in 
this  direction ;  indeed,  that  this  work  is  as  yet  in  its  infancy. 
In  truth,  the  work  done  thus  far  has  been  in  the  nature  of 
proving  that  organisms  are  regularly  connected  with  the  fer- 
mentations and  decompositions,  and  also  with  certain  processes 
of  disease,  rather  than  any  effort  to  show  how  they  bring 
about  these  results.  This  was  necessary  in  the  first  instance, 
as  the  forerunner  of  a  farther  and  more  complete  understand- 
ing of  the  subject  that  must  come  from  a  closer  study  of  the 
modes  through  which  these  low  organisms  produce  their 
effects.  It  is  plain  that  we  cannot  know  any  one  of  the  disease 
germs  until  all  of  the  products  of  its  remoleculizations  have 
been  isolated  and  studied  separate  and  apart  from  the  organism 
itself,  as  has  been  done  with  the  products  of  so  many  of  the 
higher  animals  and  plants.  I  see  no  other  plan  by  which  we 
can  ever  know  the  capabilities  and  all  of  the  possibilities  of 
micro-organisms,  in  connection  with  the  production  of  disease. 
In  most  cases  of  the  discovery  of  poisonous  properties  in  the 
higher  plants,  the  specific  product  of  the  plant  in  which  that 
poison  resides  has  proven  itself  capable  of  isolation  by  the 
means  known  to  chemists ;  and  the  disease-producing  poisons 
of  the  lower  organisms  will  do  the  same  when  the  effort  to 
find  them  has  been  prosecuted  with  sufficient  skill  and  energy. 
As  alcohol  has  been  isolated,  as  the  vegetable  alkaloids  have 


134  THE   GERM   THEORY   OF   DISEASE. 

been  isolated,  as  the  toxic  elements  of  the  waste  products  of 
animal  life  have  been  isolated,  and  as,  through  this  isolation, 
the  exact  properties  of  these  agents  have  become  known  to 
us,  so  must  sepsin  be  isolated,  so  must  the  poisonous  product 
of  the  bacillus  anthracis  (Anthracine)  be  isolated,  so!  must 
the  poisonous  principle  of  every  disease-producing  germ  be 
isolated,  and  each  of  these  studied  separate  and  apart  from 
the  organisms  which  produce  them ;  and  in  each  case  their 
properties  must  be  demonstrated  and  determined  by  direct 
experiment,  before  they  can  be  said  to  have  been  accurately 
studied,  and  that  we  know  their  properties  and  capabilities. 
This  is  the  recognized  means  of  learning  the  powers  and 
capabilities  of  the  products  of  the  higher  plants  and  animals. 
No  one  is  foolish  enough  to  deny  the  value,  the  necessity,  of 
the  knowledge  to  be  gained  by  this  mode  of  study  in  the 
vegetable  kingdom.  If  there  has  been  any  truth  arrived  at 
in  all  the  research  that  has  been  given  to  the  subject  of  the 
production  of  disease  by  the  lower  organisms,  that  truth 
requires  to  be  extended,  and  rendered  more  exact,  by  the 
modes  of  study  we  have  just  indicated. 

PHYSIOLOGICAL  CHANGES. 

The  question,  as  to  whether  the  nature  of  the  bacteria  and 
their  allied  forms  are  always  essentially  the  same,  is  one  that  is 
very  important  to  determine.  Very  many  persons  seem  to  think 
that  the  characteristics  of  this  or  that  organism  may  be  perma- 
nently changed,  by  temporary  changes  in  the  media  in  which  it  is 
grown.  This  is  a  question  of  the  gravest  importance ;  and  one 
on  which  there  has,  as  yet,  been  very  little  or  no  exact  experi- 
ment. Therefore  we  have  nothing  but  conjecture ;  unless, 
indeed,  we  may  regard  the  experiments  of  Pasteur,  in  his 
efforts  to  moderate  the  virulence  of  the  bacillus  anthracis,  the 
organism  of  chicken  cholera,  etc.,  experiments  in  this  direction. 


PHYSIOLOGICAL   CHANGES.  135 

These,  however,  certainly  cannot  be  classed  as  exact  experi- 
ments. Yet  so  far  as  they  have  scientific  value,  it  is  undoubtedly 
in  the  direction  of  the  maintenance  of  the  proposition  that  the 
nature  of  organisms  may  be  profoundly  changed  by  tempo- 
rarily changing  the  media  in  which  they  are  grown ;  for  it  is  on 
this  basis  that  we  must  account  for  changes  in  results.  Such 
a  proposition  will,  however,  require  the  most  rigid  proof  be- 
fore we  can  accept  it  as  a  modification  of  the  essential  nature 
of  the  products,  that  will  be  carried,  with  the  organism,  back 
into  the  media  froui  which  it  was  transplanted. 

The  other  proposition,  that  the  products  of  the  organism 
change  with  the  media  in  which  it  is  grown,  is  of  a  very 
different  nature,  and  much  more  plausible.  We  all  know 
that  our  own  urine  may  be  changed  from  acid  to  alkaline, 
by  certain  changes  in  diet;  that  the  amount,  and  to  some 
extent,  the  quality  of  opium,  is  affected  by  the  nature  of  the 
soil  in  which  the  plants  are  grown.  Still  it  does  not  appear 
in  these  cases  that  the  essential  features  of  the  waste  products 
are  more  than  modified  in  some  unimportant  particulars. 
The  urine  will  still  furnish  urea,  and  the  opium  will  still 
furnish  morphine,  although  each  will,  possibly,  furnish  their 
characteristic  product  in  diminished  quantity.  But  in  either 
case,  the  original  character  of  the  product  will  be  resumed 
with  the  resumption  of  the  original  diet. 

One  would  scarcely  expect  the  yeast  plant  to  produce  a 
nitrogenous  alkaloid  when  grown  in  a  pure  solution  of  sugar 
or  starch,  containing  none  of  the  element  nitrogen.  So  an 
organism  whose  normal  habitat  is  nitrogenous  compounds, 
and  whose  waste  products  are  nitrogenous,  if  transferred  and 
found  to  grow  in  pure  starch,  would  certainly  not  produce  a 
nitrogenous  alkaloid  as  a  part  of  its  waste  product,  while 
growing  in  the  starch;  yet  I  would  expect  it  to  again  produce 
the  nitrogenous  product  if  replaced  into  nitrogenous  matter ; 


136  THE   GERM   THEORY   OF   DISEASE. 

if,  indeed,  the  plant  retained  sufficient  vitality  to  perform  its 
functions.  The  material  for  the  formation  of  the  waste 
product  must  be  present  in  the  food,  otherwise  it  cannot  be 
formed.  Again,  it  may  be  that  the  remoleculization  will 
be  different  in  foods  of  a  different  nature,  even  though  the 
elements  be  all  present.  Dr.  Miller  informs  us  that,  in  his 
experiments,  he  has  found  that  the  bacterium  lactis  produced 
no  acid  when  grown  in  soup ;  but  when  a  little  sugar  or 
starch  was  added,  the  lactic  acid  was  promptly  formed.  He 
gives  us  no  intimation  of  the  nature  of  the  waste  product  of 
this  organism  when  grown  in  the  soup  not  sweetened.  This 
however,  serves  to  show  how  the  waste  product  may  be 
changed,  temporarily,  by  changes  in  the  nature  of  the  food. 
That  changes  of  this  nature  may  occur  in  a  large  number  of 
the  low  forms  of  life  seems  not  only  plausible,  but  probable. 
But  that  this  will  affect  the  nature  of  the  organism  perma- 
nently, is  another  question;  and  one  that  will  require  much 
experiment  to  prove  satisfactorily. 

MANNER  OF  ACTION. 

How  can  these  low  organisms  produce  disease?  This  ques- 
tion is  being  asked  by  many  of  the  thinking  men  of  the  world 
to-day.  Men  seem  to  be  at  a  loss  for  a  reasonable  answer; 
such  an  answer  as  will  satisfy  the  mind  that  is  earnestly  seek- 
ing an  explanation  of  the  phenomena  described  by  such  ex- 
perimentalists as  Koch  and  Pasteur.  These  men  have  not 
answered  it.  They  tell  us  what  they  have  found ;  that  certain 
phenomena  invariably  follow  the  introduction  of  certain  germs 
into  the  bodies  of  animals;  that  certain  germs  produce  certain 
diseases.  How  do  they  accomplish  this?  what  is  their  modus 
operandi?  This  question  must  have  a  reasonable  answer  be- 
fore the  germ  theory  of  disease  can  find  a  firm  basis  in  the 
minds  of  the  masses  of  men.  The  days  of  hocus-pocus  have 


MANNER   OF   ACTION.  137 

passed  away  from  the  medical  profession  forever.  A  few  men 
may  take  these  things  on  faith,  and  wait  for  time  to  develop 
the  rational  answer,  but  the  many  will  wait,  and  watch  for 
farther  developments  to  point  out  a  reasonable  and  philosophic 
answer,  before  they  will  accept  this  theory  without  reserve. 
Can  such  an  answer  be  given  with  our  present  knowledge  of 
the  subject?  If  it  be  required  that  every  step  be  proven  by 
actual  demonstrated  fact;  if  reasonable  circumstantial  evi- 
dence be  not  admitted,  only  a  few  cases  can  be  clearly  made 
out.  But  on  the  other  hand,  if  the  physiology,  as  previously 
explained,  be  accepted,  the  manner  of  the  production  of  dis- 
ease becomes  clear.  I  should  not  insist  that  the  poisonous 
substance  must,  in  every  case,  be  an  alkaloid.  But  it  must 
be  an  organic  compound  closely  akin  to  an  alkaloid.  To  say 
that  these  organisms  produce  disease,  simply  by  their  presence, 
is  not  a  sufficient  explanation.  We  all  know  that  their  pres- 
ence is  not,  in  itself,  a  sufficient  cause;  for  if  this  were  so,  one 
organism  would  be  as  potent  as  another.  And  we  all  know, 
who  have  had  any  experience  in  the  examination  of  these 
forms,  that  many  of  them  are  without  any  evil  effect  what- 
ever; that  wounds  in  the  mouth  and  elsewhere  heal  readily 
and  perfectly  when  covered  with  them.  We  also  know  that 
the  great  majority  of  the  higher  plants  are  innocent  of  any 
evil  effect  upon  the  human  system;  and  it  is  perfectly  reason- 
able that  we  should  find  the  same  differences  to  exist  among 
the  lower  plants.  Many  kinds  of  plants  grow  together  with- 
out injury  to  each  other;  but  plants  are  found  that  destroy 
their  neighbors  by  the  poisonous  effects  of  their  waste  pro- 
ducts. Then  it  seems  plain  that  the  differences  must  be  found 
in  the  peculiar  products  to  which  the  particular  organism  gives 
rise.  These  we  have  already  sufficiently  explained.  We  have, 
also,  sufficiently  explained  the  modus  operandi,  in  the  de- 
struction of  organic  substances  in  general.  They  are  simply 


138  THE   GERM   THEOEY   OF   DISEASE. 

remoleculized,  as  any  other  food  material  is  remoleculized; 
nothing  more  and  nothing  less;  and  it  is  in  the  chemical  re- 
organization of  the  elements  for  the  formation  of  the  waste 
products  that  poisons  are  evolved. 

It  seems  perfectly  natural  that  in  this  remoleculization  there 
should  ofteu  be  a  residue  that  escapes  digestion;  as  is  seen  in 
the  so-called  rotting  of  wood  and  many  other  substances.  It 
is  not  probable  that  one  organism  is  capable  of  the  complete 
destruction  of  such  substances;  but  rather,  that  many  are 
concerned  in  the  work. 

I  may  be  permitted  to  make  a  suggestion  in  regard  to  the 
cause  of  the  difference,  that  is  so  often  noticed,  of  the  com- 
parative liability  of  different  persons  to  attacks  by  these 
organisms.  Several  persons  receive  wounds.  So  far  as  can 
be  seen,  their  chances  for  a  speedy  recovery  are  equally  good  ; 
but  some  of  these  develop  sepsis,  while  others  do  not.  Now, 
much  of  this  is  explained  by  the  fact  that  we  are  unable  to 
perceive  the  entrance  of  these  organisms,  and  they  may  gain 
admission  to  the  one  and  not  to  the  other,  and  we  be  none  the 
wiser  until  we  find  that  sepsis  is  established.  This  is  always 
a  possible  explanation,  for  the  history  of  the  experimentation 
on  this  subject  shows  full  well  that  we  have  not,  even  yet, 
learned  to  prevent  the  ingress  of  these  germs  with  absolute 
certainty.  Yet  over  and  above  all  of  this,  there  is  a  certain 
residue  of  cases  that  show  that  different  persons  are  liable  in 
different  degrees  to  sepsis.  This  has  been  noticed  ever  since 
there  was  such  a  profession  as  medicine,  and  the  class  of 
patients  to  which  it  refers  have  been  pretty  closely  defined. 
They  are  those  whose  powers  of  life  have  been  weakened,  by 
whatever  cause.  This  is  said  to  be  the  resistance  of  the 
tissues  to  the  invasion  of  the  organisms.  How  do  they 
resist?  Now,  if  we  accept  the  explanation  of  the  formation 
of  the  digestive  bodies,  as  previously  explained,  this  supposi- 


MANNER   OF   ACTION.  139 

tion  becomes  tenable.     When  an  organism   or  spore  of  an 
organism  falls  upon  a  cell  or  naked  granulation  of  a  wound, 
and  finds  there  the  conditions  suitable  for  its  development,  its 
digestive  body  is  at  once  thrown  out  for  the  preparation  of 
its  food  material  which  exists  in  the  tissues  with  which  it  is 
surrounded.     This  digestive  substance  proves  irritant  to  the 
cell  upon  which  the  germ  has  fallen.     This  irritation  excites 
the  cell   to  throw   out  its   peculiar   digestive    body  for  the 
removal  of  the  irritant  with  which  it  is  beset.     Here  we  get  a 
glimpse  of  the  antagonists.     It  is  cell  against  cell ;  digestive 
body  against  digestive  body.     A  contest  has  begun.     Which 
will  win?     The  stronger,  of  course.     If  the  man  be  vigorous 
and  healthy  and  his  tissues  highly  endowed  with  the  energies 
of  life,  the  chances  are  this  much  in  his  favor ;  but  if,  on  the 
other  hand,  his  powers  of  life  be  at  a  low  ebb,  if  his  tissues 
respond  to  irritants  but  feebly,  then  the  chances  are,  this  far, 
in  the  favor  of  the  intruding  organism.     In  the  first  case,  the 
cell   upon  which   the   intruding   germ    has   fallen    responds 
promptly  to  the  irritation  ;  a  substance  calculated  to  free  it 
from  the  effects  of  the  intruder  is  formed  and  poured  out 
upon  it  and  meets  the  digestive  body  of  the  intruder,  hinder- 
ing, dissipating  and  nullifying  its  action.     In   this  way  the 
intruding  germ  is,  in    many  cases,  possibly,   overcome  and 
driven  out.     In  the  opposite  case,   where  the  vital  powers 
are  at  a  low  ebb,  the  response  to  the  irritation  is,  perhaps, 
very  sluggish,   the   digestive    body  is   poor   in  quality  and 
scanty  in   quantity,  and   the   intruding   germ   has   an   easy 
victory. 

If  we  suppose  that  the  intruder  is  a  spore,  a  seed,  with  a 
store  of  food  material  laid  up  within  its  shell,  the  case  is  not 
different  essentially.  The  history  of  the  experiment  on  this 
subject  shows  that  during  this  process  excretory  products  are 
thrown  off,  and  these  may  prove  direct  irritants  that  will 


140  THE   GERM   THEORY   OF   DISEASE. 

arouse  the  resistant  energies  of  the  tissues.  Surely,  if  the 
tissues  are  capable  of  forming,  by  reason  of  irritation,  a 
secretion  that  will  digest  a  piece  of  ivory  that  has  been  thrust 
into  the  flesh,  which  has  been  proven  by  direct  experiment, 
we  should  expect  this  kind  of  resistance  to  be  offered  to  the 
development  of  disease-producing  germs. 

Facts  of  a  very  decisive  nature  bearing  on  this  point  have 
been  brought  to  light  by  Dr.  Sternberg,  in  the  following 
experimentation,  which  I  quote  : — 

"  If  we  add  a  small  quantity  of  a  culture-fluid  containing 
the  bacteria  of  putrefaction  to  the  blood  of  an  animal,  with- 
drawn from  the  circulation  into  a  proper  receptacle,  and 
maintained  in  a  culture-oven  at  blood  heat,  we  will  find  that 
these  bacteria  multiply  abundantly,  and  evidence  of  putre- 
factive decomposition  will  soon  be  perceived.  But  if  we 
inject  a  like  quantity  of  the  culture-fluid  with  its  containing 
bacteria  into  the  circulation  of  a  living  animal,  not  only  docs 
no  increase  and  no  putrefactive  change  occur,  but  the  bacteria 
introduced  quickly  disappear,  and  at  the  end  of  an  hour  or 
two  the  most  careful  microscopical  observation  will  not  reveal 
the  presence  of  a  single  bacterium.  This  difference  we  ascribe 
to  the  vital  properties  of  the  fluid  as  contained  in  the  vessels 
of  a  living  animal;  and  it  seems  probable  that  the  little 
masses  of  protoplasm,  known  as  white-blood  corpuscles,  are 
the  essential  histological  elements  of  the  fluid,  so  far  as  any 
manifestation  of  vitality  is  concerned. 

The  writer  has  elsewhere  suggested  that  the  disappearance 
of  the  bacteria  from  the  circulation,  in  the  experiment  above 
referred  to,  may  be  effected  by  the  white  corpuscles,  which,  it 
is  well-known,  pick  up,  after  the  manner  of  amoeba?,  any  par- 
ticles, organic  or  inorganic,  which  come  in  their  way.  And 
it  requires  no  great  stretch  of  credulity  to  believe  that  they 
may,  like  an  amoeba,  digest  and  assimilate  the  protoplasm  of 


MANNER   OF   ACTION.  141 

the  captured  bacterium,  thus  putting  an  end  to  the  possibility 
of  its  doing  any  harm. 

In  the  case  of  a  pathogenic  organism  we  may  imagine  that, 
when  captured  in  this  way,  it  may  share  a  like  fate,  if  the 
captor  is  not  paralyzed  by  some  potent  poison  evolved  from  it 
(the  italics  are  mine),  or  overwhelmed  by  its  superior  vigor 
and  rapid  multiplication.  In  the  latter  event,  the  active  career 
of  our  conservative  white  corpuscle  would  be  quickly  term- 
inated, and  its  protoplasm  would  serve  as  food  for  the  enemy. 
It  is  evident  that  in  a  contest  of  this  kind  the  balance  of 
power  would  depend  upon  circumstances  relating  to  the  in- 
herited vital  characteristics  of  the  invading  parasite  and  of  the 
invaded  leucocyte." 

In  these  paragraphs  we  have  the  strongest  evidence  of  the 
truth  of  the  supposition  stated,  of  the  nature  of  the  combat 
between  the  tissues  or  the  white  corpuscles  of  the  blood  and 
the  wandering  cells  for  the  tissues,  on  the  one  hand,  and  the 
invading  organisms  on  the  other.  The  writer,  though  not 
intending  to  put  forward  his  own  experimentation  in  this 
work,  may  say  that  he  has  also  seen  strong  evidence  of  the 
truth  of  this  in  tissue  taken  directly  from  man  to  the  warmed 
stage  of  the  microscope,  in  which  the  wandering  cells  were 
found  loaded  with  micrococci,  which  in  many  instances  seemed 
to  be  destroying  the  cells.  Some  were  motionless  and  filled 
to  overflowing  with  the  organisms,  with  little  chains  of  the 
micrococci  extending  from  them,  while  others  containing 
but  few  of  the  organisms  exhibited  their  usual  motions.  This 
phenomenon  may  occasionally  be  demonstrated  in  the  peculiar 
granulations  which  are  sometimes  found  under  plates  for 
artificial  teeth,  where  the  gums  have  taken  on  a  bad  condi- 
tion. 

Dr.  Koch  has  also  seen  micrococci  in  the  white  blood  cor- 
puscles, under  circumstances  that  indicated  that  the  blood  cells 


142  THE   GERM    THEORY    OF    DISEASE. 

were  being  destroyed  by  them.  He  says:  "Their  relation 
to  the  white  blood  corpuscles  is  very  peculiar.  They  penetrate 
into  these  and  multiply  in  their  interior.  One  often  finds 
that  there  is  hardly  a  single  white  corpuscle  in  the  interior  of 
which  bacilli  cannot  be  seen.  Many  contain  isolated  bacilli 
only;  others  have  thick  masses  in  their  interior,  the  nucleus 
being  still  recognizable;  while  in  others  the  nucleus  can  no 
longer  be  distinguished;  and  finally,  the  corpuscle  may  become 
a  cluster  of  bacilli,  breaking  up  at  the  margin — the  origin  of 
which  one  could  not  have  explained  had  there  been  no  oppor- 
tunity of  seeing  all  the  intermediate  steps  between  the  intact 
white  corpuscles  and  these  masses." 

With  these  facts  before  us,  and  with  the  plain  teachings  of 
the  relations  of  the  life  force  to  matter,  as  exemplified  in  the 
phenomena  of  digestion,  nutrition  and  the  formation  of  waste 
products,  it  seems  to  me  we  must  not  fail  to  gain  an  under- 
standing of  these  processes.  The  cells  attacked,  either  digest 
the  invading  germs,  or  the  invading  germs  digest  them.  And 
here,  as  everywhere  else  in  nature,  the  stronger  will  be'  the 
victor.  In  other  cases,  as  in  septicaemia,  the  excretions  of  the 
bacilli  do  not  seem  to  produce  such  marked  local  lesions,  but 
the  waste  products  of  the  organisms  are  absorbed  and  act  the 
part  of  a  diffusible  poison,  producing  the  general  symptoms 
manifested  in  these  cases. 

Again,  the  history  of  cases  shows  that  sepsis  is  most  liable 
to  occur  in  the  early  time  of  the  healing  of  wounds;  at  a  time 
when  the  tissues  may  be  supposed  to  be  still  suffering  from 
the  effects  of  the  shock.  In  this  case  it  must  be  supposed 
that  the  tissues  are  not  so  well  able  to  contend  with  the 
intruding  germs  as  they  are  afterward,  when  the  process  of 
granulation  is  going  forward  vigorously. 

We  have  also  experimental  evidence  establishing  this  point. 
Sonnenschein  found  that  certain  bacteria  with  which  he  was 


INFLAMMATIONS.  143 

experimenting  failed  to  grow  in  the  tissues  of  an  animal. 
Believing,  from  the  results  of  previous  experimentation,  that 
sepsin  injected  with  the  hacteria  favored  their  development, 
and  having  found  the  effects  of  sepsin  similar  to  that  of  sul- 
phate of  atropia,  he  injected  a  small  amount  of  that  drug  with 
the  organisms  and  found  that,  under  these  conditions,  they 
grew  and  produced  sepsis.  It  is  difficult  to  see  how  the  sul- 
phate of  atropia  could  aid  the  bacteria  otherwise  than  by 
paralyzing  the  tissues  temporarily,  preventing  their  resistance 
until  the  organisms  had  established  themselves.  A  number 
of  other  experiments  have  developed  facts  of  a  similar  nature. 
Gradle  says,  page  123,  "  We  do  not  know  whether  putre- 
factive bacteria  exert  any  direct  influence  upon  the  exposed 
tissues.  Even  if  that  be  not  the  case,  the  products  of  decom- 
position which  they  engender  irritate  the  wound  in  an  unmis- 
takable manner.  This  is  seen  in  the  redness  and  sensitiveness 
of  the  margins  of  the  wounds.  .  ...  These  bacteria 
are  always  overcome  by  the  tissues." 

INFLAMMATIONS. 

The  question  as  to  whether  we  ever  have  the  formation  of 
pus  without  the  presence  of  micro-organisms,  has  been  much 
discussed,  pro  and  con,  of  late  years,  by  men  standing  high 
in  the  medical  profession.  It  has  even  been  contended  that 
we  never  have  inflammation  without  them,  notwithstanding 
the  well-known  effects  of  the  blister  and  the  mustard  plaster. 
Did  it  ever  occur  to  any,  that  in  the  blister  and  the  mustard 
plaster,  we  are  making  use  of  an  irritant  that  has  been  pre- 
pared for  us  by  the  life  force,  and  is,  to  say  the  least,  closely 
akin  to  the  irritant  that  we  would  expect  from  the  disease- 
producing  organisms?  But  have  we  not  mineral  irritants, 
and  may  we  not  produce  inflammation  by  their  use?  Is  not 
pus  a  result  of  inflammation  ?  I  am  not  unmindful  of  the 
fact  that  there  are  several  theories  explaining  the  production 


144  THE    GERM    THEORY    OF    DISEASE. 

of  pus;  and  that  pus  does  occur  under  some  conditions  in 
which  the  presence  of  inflammation,  at  any  time  previous  to 
its  formation,  is  extremely  difficult  of  demonstration.  Yet 
I  am  of  the  opinion  that  there  are  very  few  surgeons  to-day 
who  do  not  regard  the  formation  of  pus  as  one  of  the  results 
of  inflammation,  and  who  will  not  naturally  expect  the 
formation  of  pus  to  result  in  case  of  prolonged  and  intense 
inflammatory  action. 

Still,  the  formation  of  pus  does  not  necessarily  occur  as  a 
result  of  every  severe  inflammatory  state;  and  some  recent 
experiments  by  M.  I.  Straus  and  others,  in  both  France  and 
Germany,  seem  to  show  that  pus  will  not  form  in  inflammation 
artificially  excited,  if  micro-organisms  be  excluded.  Other 
experimenters  have  had  other  results,  and  the  question  is  not 
yet  settled  by  the  experimental  method ;  and  we  might  with 
some  reason  say  that  it  cannot  be  so  settled,  until  the  methods 
of  experimentation  approach  more  nearly  perfection  than  they 
seem  to  be  at  the  present  time. 

However,  just  so  long  as  we  regard  the  formation  of  pus 
to  be  a  result  of  inflammation,  must  we  expect  that  pus  will 
be  formed  without  the  presence  of  micro-organisms.  If  this 
is  not  the  true  explanation  of  this  phenomenon,  if  future 
developments  should  demonstrate  that  these  two  processes  are 
not  related  to  each  other  as  cause  and  effect,  then  it  may, 
possibly,  be  shown  that  pus  cannot  form  without  the  presence 
of  micro-organisms. 

At  the  same  time  it  must  be  admitted  that  the  formation  of 
pus  is  generally  accompanied  by  the  development  of  micro- 
organisms, and  that  their  presence  facilitates  pus  formation. 
This  is  clearly  the  result,  not  of  temporary,  or  a  single  appli- 
cation of  an  irritant,  but  of  the  continuous  irritation  by  the 
secretion  or  excretion  continuously  given  out  by  the  organ- 
isms ;  and  we  have  no  reason,  that  I  know  of,  to  suppose  that 
the  result  would  be  much  different  if  the  same  products  of 


BLOOD   DISEASES.  145 

these  life  forms  could  be  gathered  and  continuously  distributed 
in  the  tissues  artificially. 

In  many  of  Straus'  experiments,  and  others  of  this  class 
referred  to  above,  agents  were  introduced  that  evidently 
paralyzed  the  tissues,  and  as  pus  formation  is  a  vital  act,  it 
was  necessarily  prevented.  Every  such  element  must  be 
rigorously  excluded  from  our  experimentation  before  the 
results  can  be  depended  upon  as  conclusive. 

BLOOD  DISEASES. 

The  production  of  disease,  however,  is  not  limited  to  in- 
flammation and  pus  formation.  Many  of  the  diseases  now 
supposed  to  be  parasitic  in  their  causation  are  not  essentially 
inflammatory,  but  are  known  as  systemic  or  blood  diseases. 
This  class  of  diseases  are  not  caused  by  any  simple  irritant,  but 
by  some  toxic  element  developed  by  the  organisms.  As  to 
what  this  toxic  element  may  be  we  have  only  conjecture,  but 
after  what  we  have  just  said  in  reviewing  the  waste  products 
of  the  various  life  forms,  this  conjecture  is  a  close  approach 
to  knowledge.  The  elements  of  the  compounds  are  pretty 
certain  to  be  written  C  H  N  O,  in  varying  equivalents.  It  is 
possible  that  the  N  may  be  left  out  of  some,  or  that  the  O 
may  be  left  out  of  others.  But  this  is  not  very  probable. 
We  know  enough  of  the  alkaloids,  to  know  that  they  may 
become  a  potent  cause  of  disease,  if  developed  continuously 
in  the  blood  or  tissues. 

It  may  be  said  that  we  know  of  no  alkaloids  that  will 
produce  the  effects  shown  in  the  diseases  that  we  see 
around  us.  This  is  very  true.  A  few  years  ago  we  knew 
of  no  alkaloid  that  would  produce  the  effect  of  woorara,  or 
quinine,  or  atropine,  or  strychnia;  and  when  we  have  dis- 
covered others,  and  have  learned  their  effects,  they  will  be  as 
easily  understood  as  those  now  known  to  us.  That  systemic 
disease  may  result  in  this  way,  is  not  only  possible,  but  it 


146  THE   GERM   THEORY   OF   DISEASE. 

seems  very  probable  that  this  will  be  the  final  solution  of 
the  problem.  Indeed,  we  may  say  that  from  all  that  is  now 
known,  this  seems  certain.  But  it  is  not  from  the  formation 
of  the  alkaloids  alone  that  we  will  find  these  effects  produced. 
The  organic  acids  will  be  found  to  have  their  share  in  the 
work;  also  various  irritants,  and  the  digestive  bodies  de- 
veloped by  the  organisms.  It  will  be  found  that,  all  of  these 
products  are  formed  together  and  do  their  work  together, 
producing  the  complex  results  that  we  see  in  the  complicated 
forms  of  disease  so  frequently  met  with. 

While  the  mere  physical  presence  of  organisms  will  in  no 
case  account  for  the  effects  ascribed  to  them  in  the  production 
of  disease,  they  cannot  be  entirely  ignored.  When  bacteria 
or  micrococci  are  gathered  together  in  groups  and  large 
masses  (zooglia)  in  the  tissues,  they  will  certainly  have  some 
evil  influence  by  their  mere  presence  in  such  situations, 
especially  when  this  happens  to  be  in  important  organs. 
Also,  the  fixed  material  laid  up  in  these  cells  may,  after  the 
death  of  the  organisms,  have  its  influence.  But  I  am  per- 
suaded that  neither  of  these  causes  is  the  potent  factor  in  the 
production  of  disease. 

I  would  not  have  you  suppose,  however,  that  we  can  have 
no  disease  without  micro-organisms.  Man  may  be  abused  by 
the  life  forms  around  him,  and  man  may  abuse  himself.  He 
may  eat  too  much  good  food  and  suffer  in  consequence.  He 
may  injudiciously  expose  himself  to  the  inclemencies  of  the 
weather,  and  start  serious  inflammation  of  important  organs. 
He  may  exhaust  his  energies  by  overwork,  and  suffer  all  the 
consequences  that  anaemia  brings  in  its  terrible  train.  He 
may  suffer  from  faults  in  the  physiological  activity  of  his 
own  tissues,  from  neoplasms,  as  cancer  sarcoma,  lipoma,  and 
very  many  other  affections  that  the  micro-organisms  do  not 
have  to  answer  for. 


APPENDIX. 


DENTAL  CARIES. 


ITS    EELATIONS  TO  THE    GERM  THEORY  OF 
DISEASE. 

Many  theories  have  been  advanced,  in  times  past,  to  account 
for  caries  of  the  teeth.  Most  of  these  have  been  vague  and 
indefinite,  and  have  passed  away  with  the  advance  of  time. 
About  the  beginning  of  the  present  century  the  vital  theory, 
as  it  was  called,  was  prominent.  By  those  who  held  this 
theory,  caries  was  supposed  to  result  from  an  inflammation  of 
the  structure  of  the  dentine,  which  terminated  in  the  final 
breaking  down  of  the  part ;  and  as  this  structure  is  incapable 
of  physiological  repair,  a  cavity  was  the  inevitable  result. 
This  theory  seems  to  have  been  very  thoroughly  disproved  by 
the  following  considerations.  It  was  observed  that  artificial 
teeth,  constructed  of  ivory,  bone,  sheep's  teeth  and  human 
teeth,  were  as  liable  to  caries  as  the<natural  teeth  ;  and  that 
this  decay  was,  to  all  appearance,  the  result  of  similar,  if  not 
precisely  the  same  causes.  This,  of  course,  could  not  be  the 
result  of  vital  forces  existing  in  the  structure  undergoing  the 
process  of  decay.  The  conditions  of  the  decaying  portions 
were  very  closely  studied,  to  see  whether  or  not  anything 
could  be  discovered  that  would  show  that  these  processes  were 
essentially  different  from  each  other.  Some  differences  were 
found,  but  the  more  they  were  studied  the  more  evident  did 
it  seem  that  these  differences  were  not  of  such  a  nature  as  to 
show  that  the  processes  were  in  any  wise  distinct  from  each 
other.  These  studies  caused  the  abandonment  of  the  vital 
theory;  for,  if  dead  substances  decayed  the  same  as  living 
ones,  the  forces  which  bring  about  the  result  must  be  other 

149 


150  THE   GERM   THEORY   OF   DISEASE. 

than  the  vitality  of  the  suffering  organ,  and  therefore  cannot 
be  the  result  of  inflammation;  it  must  be  some  force  external 
to  the  tooth,  something  which  attacks  the  tooth  from  without. 
This  point  seems  to  have  been  very  thoroughly  established, 
and  we  supposed  it  was  well  settled  in  the  minds  of  all 
modern  thinking  men.  But,  curiously  enough,  the  old  notion 
has  recently  been  revived  by  certain  gentlemen  in  New  York. 
The  effort  to  maintain  such  an  hypothesis,  however,  must 
inevitably  result  in  failure ;  for  in  it  there  is  a  plain  want  of 
consideration  of  the  known  facts  of  the  subject.  It  need  not, 
therefore,  detain  us  longer. 

Caries  of  the  teeth  has  been  defined  as  a  molecular  disinte- 
gration of  the  tooth's  substance,  or  a  breaking  down  of  the 
chemical  constituents  of  the  tooth,  molecule  by  molecule. 
This  destruction  always  has  its  beginning  on  the  surface  of 
the  tooth,  or  in  some  pit,  crevice,  or  other  imperfection  in  the 
enamel.  And  it  spreads  from  this  point,  as  the  focus,  in 
every  direction,  the  dentine  being  destroyed  more  rapidly 
than  the  enamel ;  hence,  it  usually  happens  that  the  cavity  is 
larger  within  than  on  the  surface  of  the  tooth.  Caries  does 
not  seem  to  be  a  simple  solution  of  the  tooth's  substance; 
sometimes  we  find  nearly  all  of  the  material  removed  from 
the  cavity,  in  other  cases  we  find  the  dentine  reduced  to  a 
pulpy  or  semi-gelatinous  mass,  in  which  the  structure  of  the 
dentine  is  more  or  less  perfectly  preserved.  Some  decays  are 
white,  some  are  black,  some  have  a  yellow  tinge — all  the 
shades  from  white  to  black  may  be  found.  But  it  was  not 
my  intention  to  give  a  lengthy  description  of  the  results  of 
caries,  but  rather  to  confine  myself  as  closely  as  possible  to 
the  discussion  of  the  probable  cause  of  the  affection  ;  I  say 
probable  cause,  for  I  do  not  assume  that  the  cause  or  causes 
are  certainly  known.  Indeed,  we  may  say  that  at  the  present 
time  there  is  the  greatest  disagreement  among  even  the  best 


DENTAL    CAEIES.  151 

informed  men  on  this  important  subject;  and  that  it  is  still 
very  uncertain  that  any  of  the  theories  in  regard  to  the  matter 
are  correct.  It  is  proper  that  I  should  say,  however,  that 
more  than  one  of  these  explain  the  phenomena  with  sufficient 
accuracy  to  be  of  great  value,  both  in  the  prevention  and 
treatment  of  this  affection.  It  must  not  be  supposed  that  a 
theory  must  be  absolutely  correct  to  be  of  use.  Theories  are 
usually  contrived  in  the  effort  to  explain  phenomena,  and  it 
often  happens  that  a  false  theory  leads  to  as  good  an  applica- 
tion of  means  to  ends  as  the  true  one  would  do.  Of  this, 
however,  we  can  never  have  any  assurance;  therefore,  as  long 
as  there  is  a  reasonable  doubt  the  search  for  the  truth  should 
continue. 

The  theory  for  the  explanation  of  caries  which  has  received 
the  greatest  attention  and  the  widest  recognition  in  modern 
times,  is  what  is  known  as  the  acid  theory.  This  theory  seems 
to  account  for  the  phenomena  more  perfectly  than  any  other 
that  has  as  yet  attained  prominence  in  the  minds  of  thinking 
men.  As  a  working  theory,  a  basis  upon  which  to  found 
principles  of  treatment,  it  has  undoubtedly  been  the  means  of 
good.  Yet,  in  the  scientific  aspect  of  the  subject,  there  is 
much  objection  to  be  urged  against  it.  A  very  large  amount 
of  work  has  been  done  with  the  view  of  demonstrating  the 
absolute  truth  of  this  theory,  all  of  which  must  be  regarded 
as  a  failure,  so  far  as  the  attainment  of  that  particular  object 
is  concerned.  The  labor  has  not  been  lost,  however;  but,  on 
the  other  hand,  has  been  of  immense  value.  It  is  this  labor, 
the  basis  of  fact  which  it  has  brought  to  light,  that  will  be  of 
most  service  to  us  in  the  building  up  of  other  theories  for  the 
explanation  of  the  phenomena,  which  may  serve  us  usefully, 
until  such  time  as  theories  shall  be  displaced  by  demonstra- 
tion, the  goal  to  which  we  are  all  looking  forward. 

According  to  the  chemical   theory,  the  substance  of  the 


152  THE    GERM   THEORY   OF   DISEASE. 

tooth  is  decomposed  by  an  acid ;  this  acid  acts  more  readily 
on  dentine  than  upon  the  enamel,  therefore  the  tendency  to 
the  enlargement  of  the  cavity  toward  the  internal  portions  of 
the  tooth.  Some  writers,  as  Dr.  Watt,  have  attempted  to 
define  the  acids  thus  acting,  and  to  divide  decays  into 
classes,  according  as  this  or  that  acid  is  active  in  its  produc- 
tion. The  acids  that  have  been  thus  pointed  out  are:  Nitric 
acid  (white  decay),  Sulphuric  acid  (black  decay)  and  Chloro- 
hydric  acid  (intermediate  colors). 

Most  of  those  who  have  written  on  this  subject,  however, 
have  been  content  without  specifying  the  particular  acids  so 
definitely;  while  some  have  been  of  the  opinion  that  these 
particular  acids  have  little  or  nothing  to  do  with  the  matter, 
and  seek  to  show  that  other  acids  are  more  likely  to  do  the 
ugly  work. 

The  origin  of  the  acids  which  produce  caries  has  been  a 
subject  of  much  inquiry.  A  great  amount  of  labor  has  been 
bestowed  upon  this  point.  It  has  been  supposed  that  the 
saliva  contained  it,  and  very  careful  examinations  have  been 
made  in  this  direction,  which  have  contributed  to  our  know- 
ledge of  this  secretion,  but  have  thrown  very  little  light  on 
the  point  in  issue,  other  than  to  demonstrate  that  the  cause 
of  decay  is  not  to  be  found  in  this  direction.  It  has  shown 
that  decay  occurs  in  mouths  in  which  the  saliva  is  habitually 
normal;  and  that  decay  does  not  occur  in  some  mouths  in 
which  the  saliva  is  habitually  acid. 

The  hypothesis  that  the  acid  is  furnished  upon  the  spot, 
through  the  decomposition  of  the  food  lodging  between  the 
teeth,  or  in  crevices  and  imperfections  in  the  enamel,  seems 
much  more  feasible,  and  gives  a  much  more  satisfactory 
explanation  of  the  phenomena.  According  to  this  hypothesis, 
the  acid  is  formed  in  juxtaposition  with  the  portion  of  the 
tooth  suffering  from  its  effects,  even  within  the  cavity  itself, 


THE  GERM  THEORY  OF  CARIES.          153 

while  the  general  fluids  of  the  mouth  may  be  neutral,  or 
even  alkaline. 

The  manner  of  the  production  of  this  acid  has  been  a 
subject  of  much  inquiry.  All,  I  believe,  admit  that  it  must 
come  in  some  way  through  fermentation  or  decomposition  ; 
at  any  rate,  through  a  rernoleculization  of  the  substances 
lodged  about  the  teeth.  This  leads  directly  to  the  discussion 
of  the  much  vexed  question  of  the  fermentations  and  de- 
compositions, and  the  relations  of  the  life  force  thereto.  The 
research  of  the  last  few  years  leaves  but  little  doubt  on  this 
point.  These  processes  are  the  result  of  the  activity  of  living 
organisms.  The  teachings  of  Liebig  on  this  subject  may  now 
be  regarded  as  disproved.  With  this  point  settled,  the  old 
acid  theory  glides  easily  into  the  new  germ  theory,  and  we 
may  recommence  our  studies  from  the  new  standpoint  we 
have  gained,  carrying  with  us  all  the  facts  that  have  been 
developed  to  guide  us  on  our  way. 

In  the  study  of  this  subject  many  new  questions  spring  to 
the  front,  and  demand  a  hearing.  Most  of  these  have  been 
discussed  in  a  former  lecture ;  but  it  now  remains  for  us  to 
study  their  application  to  this  particular  subject.  Before 
doing  this,  however,  it  will  be  well  for  us  to  make  a  hasty 
review  of  the  discussions  that  have  been  had  in  comparatively 
recent  times  on  this  point. 

THE  GERM  THEORY  OF  CARIES. 

Who  may  have  first  suggested  that  caries  of  the  teeth  is 
caused  by  living  germs,  I  have  no  definite  knowledge.  The 
first  work  of  importance  upon  this  subject  was  by  Lieber  and 
Rottenstein,  in  Germany,  which  appeared  in  1868.  These 
gentlemen,  in  the  prosecution  of  their  studies  of  this  question 
came  to  the  conclusion  that  caries  must  result  from  the 
activity  of  micro-organisms  through  the  production  of  acids. 


154  THE   GERM   THEORY   OF   DISEASE. 

This  acid  was,  of  course,  produced  in  the  process  of  fermenta- 
tion; but  in  the  light  of  the  developments  of  the  last  few 
years,  their  observations  seem  vague  and  very  indefinite. 
They  attributed  this  result  to  leptothrix  buccalis.  The  ob- 
servations upon  which  their  views  were  based  were  given  at 
length ;  so  that  we  are  able  to  follow  them  through  all  their 
operations,  and  from  the  care  with  which  these  were  con- 
ducted, judge  of  the  merits  of  their  deductions  from  them. 
When  we  pass  their  work  in  review  carefully,  we  must  admit 
that  it  is  wanting  in  that  extreme  care  that  is  necessary  in 
investigations  of  this  delicate  nature;  especially  is  this  the 
case  when  we  examine  the  work  in  the  light  that  succeeding 
years  have  thrown  upon  investigations  of  this  class.  In  fact, 
the  modes  employed  in  such  work  have  been  completely 
revolutionized  since  this  work  appeared ;  and  as  the  general 
nature  of  such  work  has  been  discussed  in  a  previous  lecture, 
and  its  progress  described,  it  need  not  detain  ns  now. 

Notwithstanding  the  evident  errors  of  the  work  of  Lieber 
and  Rottenstein,  it  undoubtedly  made  a  deep  impression  on 
the  thought  of  the  dental  profession ;  and  this  question  has 
not  been  lost  sight  of  for  an  instant.  While  the  opinions 
given  were  not  accepted,  and  were,  apparently,  quickly  dis- 
proved, it  lent  an  impetus  to  the  study ;  and  though  no  great 
work  has  appeared,  it  has  been  progressing  in  an  intermittent 
way,  until  now  the  profession  seem  to  be  ready  to  receive  any 
work  on  this  subject  that  will  bear  reasonably  rigid  criticism. 
Such  a  work  is,  fortunately,  now  appearing,  from  the  pen  of 
Dr.  Miller,  who,  though  an  American,  is  working  in  the 
laboratory  of  Dr.  Koch  of  Berlin.  Dr.  Miller  is,  fortunately, 
in  the  very  best  position  possible  for  the  performance  of  this 
difficult  form  of  investigation ;  and  the  papers  that  have 
already  appeared  from  his  pen  give  much  encouragement  that 
he  will  succeed  in  working  out  this  subject,  and  in  giving  us 


THE   GERM   THEORY   OF   CARIES.  155 

the  underlying  facts  that  have  so  long  enshrouded  the  cause 
of  caries  of  the  teeth  in  mystery. 

But  in  this  we  are  anticipating.  There  is  another  work 
which  demands  examination  before  we  pass  to  this.  The 
views  of  Dr.  Watt  have  received  much  commendation  in  this 
country,  but  not  so  in  the  old.  There,  other  men  have  been 
prominent,  and  we  find  that  while  they  have  agreed  in  the 
main,  there  are  important  differences  between  them.  As  we 
have  said,  Dr.  Watt  has  maintained  that  decay  is  caused  by 
the  acids,  nitric,  hydrochloric  and  sulphuric,  with  possibly 
others.  In  Europe  the  influence  of  these  particular  acids 
has  been  very  generally  denied ;  and  the  results  attributed  to 
other  acids,  as  the  lactic,  acetic,  and  the  group  known  as  the 
organic  acids.  Among  those  that  have  examined  this  subject, 
none,  perhaps,  have  attained  a  wider  hearing  than  Magitot, 
of  Paris.  This  gentleman  published  a  work  on  this  subject 
in  1868,  in  which  he  makes  an  extended  examination  of  the 
subject,  arriving  at  the  conclusion  that  decay  is  caused  by 
acids.  These  acids,  however,  are  derived  from  the  saliva 
through  the  process  of  fermentation.  Dr.  Magitot  instituted 
a  long  series  of  experiments  to  determine  the  effects  of  the 
suspected  acids  on  the  teeth.  This  series  of  experiments  show 
that  most  of  the  organic  acids  act  very  feebly  on  the  teeth 
in  the  proportion  of  one  to  one  thousand  of  water;  and  that 
in  the  proportion  of  one  to  one  hundred  they  act  quite 
energetically ;  so  that  the  teeth  submitted  to  their  action  will 
be  completely  decalcified  within  a  few  weeks  or  months. 
Most  of  this  series  of  experiments  were  continued,  however, 
for  two  years.  The  conclusion  seems  to  be  that  caries  may  be 
produced  by  any  of  the  group  of  acids  that  may  be  developed 
by  the  fermentation  of  the  saliva ;  these  are  the  lactic,  acetic, 
butyric,  etc. 

Dr.  Magitot  states  distinctly,  that   the   agency  of  micro- 


156  THE   GERM   THEORY   OF   DISEASE. 

organisms  in  the  production  of  these  acids  is  admitted  by 
him,  but  discusses  this  phase  of  the  subject  no  farther.  He 
makes  no  effort  to  determine  to  what  extent  these  acids  may 
be  formed  in  the  mouth.  All  of  his  experiments  were  tried 
out  of  the  mouth,  and  no  provision  whatever  was  made  to 
ascertain  the  effect  that  fermentation  may  have  had  on  his 
solutions  in  the  progress  of  his  experimentation.  This  being 
the  case,  the  only  result  of  the  experiments  is  the  determina- 
tion of  the  strength  of  the  solutions  of  these  different  acids 
necessary  to  decalcify  a  tooth. 

This,  together  with  the  facts  obtained  from  other  sources, 
showing  that  most  of  these  acids  are  the  products  of  certain 
fermentations  that  may  go  on  in  the  mouth,  gives  much  force 
to  Dr.  Magi  tot's  conclusions. 

Very  soon  after  Dr.  Magitot's  work,  in  the  same  year, 
indeed,  came  the  work  of  Lieber  and  Rottenstein,  to  which 
we  have  referred.  The  work  seems  to  have  been  written  for 
the  express  purpose  of  showing  that  decay  of  the  teeth  is 
caused  by  the  life  and  development  of  the  fungus  known  as 
leptothrix  buccalis.  In  this  the  authors  seem  to  have  signally 
failed.  They  certainly  make  but  little  advance  toward  the 
demonstration  of  the  parasitic  theory  of  this  affection.  Indeed, 
they  do  not  seem  to  have  endeavored  to  show  that  this  fungus 
does  more  than  promote  decay  that  has  already  become 
established. 

They  say,  after  having  made  an  extensive  examination  of 
the  life  and  growth  of  the  leptothrix,  "  from  what  has  been 
said,  it  results  that  two  principal  phenomena  manifest  them- 
selves in  the  formation  of  dental  caries,  viz.,  the  action  of 
acids,  and  the  rapid  development  of  a  parasitic  plant,  the 
leptothrix  buccalis."  They  do  not  suppose  the  leptothrix 
buccalis  capable  in  itself  of  attacking  the  teeth,  if  their  con- 
dition be  normal,  but  when  their  surfaces  are  once  softened 


THE   GERM   THEORY   OF   CARIES.  157 

by  acids,  then  the  fungus  may  penetrate  the  portions  thus 
softened  and  continue  the  destruction.  Again,  they  say,  "  It 
see~ras  that  the  fungi  are  not  able  to  penetrate  an  enamel  of 
normal  consistency.  The  dentine  itself,  in  its  normal  condi- 
tion of  density,  offers  great  difficulties  to  their  entrance,  and 
we  are  not  yet  sure  that  the  leptothrix  could  triumph  over 
this  resistance."  Again,  "  We  cannot  decide  at  present  if 
the  leptothrix  is  able  to  penetrate  sound  dentine,  when  from 

nny  circumstance  it  happens  to  be  denuded 

But,  if  the  enamel  or  dentine  are  become  less  resistant  at 
any  point,  through  the  action  of  acids,  or  if,  at  the  surface  of 
the  dentine,  a  loss  of  substance  has  occurred,  then  the  elements 
of  the  fungus  can  pass  into  the  interior  of  the  dental  tissues, 
and  produce  by  their  extension,  especially  in  the  dentine, 
effects  of  softening  and  destruction  much  more  rapid  than 

the  action  of  acids  alone  is  able  to  accomplish 

The  participation  of  the  fungus  is  constant  in  the  progress 
of  caries  which  has  reached  this  stage.  As  soon  as  a  loss 
of  substance  can  be  shown,  there  is  found  the  presence  of 
the  fungus,  so  that  the  question  whether  or  no  the  acids 
alone  could  produce  ravages  more  considerable  is  without 
importance." 

The  modus  operandi  by  which  leptothrix  may  produce 
softening  of  the  dentine  is  left  without  explanation.  We  can 
conceive,  however,  that  they  may  do  something  to  assist  the 
softening  process  by  the  outpouring  of  a  digestive  fluid.  If, 
however,  this  fungus  gave  a  fluid  that  would  digest  a  tooth, 
we  would  think  that  sound  teeth  would  be  very  scarce,  for  it 
grows  abundantly  in  every  mouth. 

Since  the  time  of  Lieber  and  Rottenstein's  work  we  remem- 
ber of  no  other  of  much  importance  having  appeared  on  this 
subject.  The  discussion  has  continued,  however,  in  the  jour- 
nals. We  cannot  now  undertake  to  review  this  literature, 


158  THE   GERM   THEORY   OF   DISEASE. 

interesting  as  it  would  be,  but  must  content  ourselves  with 
one  writer,  Dr.  Miller,  now  of  Berlin. 

Dr.  Miller's  experiments  bear  the  stamp  of  being  more 
carefully  performed  than  any  that  have  previously  come  to 
our  knowledge.  This  was  to  have  been  expected,  from  the 
fact  that  they  are  the  latest,  giving  the  experimenter  the 
advantage  of  all  that  has  gone  before;  and  for  the  reason 
that  he  is  very  favorably  placed  for  such  work,  being  in  the 
midst  of  the  best  experimenters  of  the  world.  Therefore  his 
work  is  looked  to  with  unusual  interest. 

We  need  not,  however,  notice  any  but  his  last  series  of 
articles,  that  which  is  now  appearing.  We  cannot,  of  course, 
criticise  Dr.  M/s  work  now,  for  we  have  not  heard  him 
through  ;  but  enough  has  appeared  to  show  very  clearly 
what  the  result  will  be. 

Dr.  M.  begins  this  series  of  articles  with  this  sentence: 
"  During  the  last  two  years  I  have  stated  at  different  times 
and  places,  as  the  result  of  many  experiments,  that  'the  first 
stages  of  dental  caries  consist  in  a  decalcification  of  the  tissues 
of  the  teeth  by  acids,  which  are,  for  the  greater  part,  generated 
in  the  mouth  by  fermentation.7  The  object  of  the  investiga- 
tions described  in  this  and  the  following  papers,  is  to  deter- 
mine this  ferment,  and  the  conditions  essential  to  its  action." 

We  see  from  this,  that  Dr.  Miller  begins  just  where  Dr. 
Magitot  left  off  sixteen  years  ago.  The  discussion  of  the 
subject  during  these  years  has  given  us  no  additional  facts,  as 
to  the  essential  nature  of  these  phenomena ;  but  the  advance 
of  thought  in  reference  to  the  general  subject  of  such  investi- 
gations has  been  such  that  no  man  would  now  repeat  Dr. 
Magitot's  course  of  experimentation  with  the  same  end  in 
view. 

I  will  give  a  very  brief  synopsis  of  Dr.  M.'s  course.  And 
while  I  do  so,  I  wish  you  to  keep  in  mind  the  object  he  has  in 


THE   OERM   THEORY   OF   CARIES.  159 

view.  It  is  admitted  that  decay  is  brought  about  by  acids, 
developed,  or  Dr.  M.  supposes  them  to  be  developed  by  fer- 
mentation of  some  kind.  The  object  of  this  course  of  experi- 
ments is  to  find  and  examine  this  supposed  ferment. 

It  is  not  necessary  that  I  should  describe  in  detail  all  the 
apparatus  with  which  the  experimenter  provided  himself;  it 
is  sufficient  to  say  that  all  the  appliances  for  the  prevention 
of  error  were  used.  The  first  question  to  determine  was 
whether  or  not  the  ptyaline  of  the  saliva  could  so  change 
starch  as  to  produce  an  acid.  This  question  was  soon  decided 
in  the  negative.  The  starch  was  promptly  changed  into  sugar, 
but  here  the  reaction  ceased ;  the  fluid  remained  permanently 
sweet  when  the  proper  precautions  were  observed  to  prevent  the 
ingress  of  germs.  This  proves  that  the  acidifying  power  does 
not  belong  to  the  saliva.  It  must  then  be  something  foreign. 

Now,  a  freshly  extracted  carious  tooth  was  taken,  all  food 
removed,  the  outer  portions  of  the  decayed  mass  saturated 
with  a  ninety  per  cent,  solution  of  carbolic  acid,  to  destroy 
any  accidental  germs  that  might  be  in  this  portion.  Then, 
with  an  instrument,  purified  by  heat  after  each  cut,  layer 
after  layer  of  the  softened  dentine  was  removed  until  the 
inner  portions  were  reached.  Then  a  slice  was  quickly  con- 
veyed to  a  sterilized  culture  medium,  composed  of  sterilized 
saliva,  water,  sugar  and  starch,  and  placed  in  an  incubator, 
together  with  another  test-tube  of  the  same  culture  fluid  un- 
infected,  to  serve  as  a  check.  In  twenty-four  hours  the 
infected  culture  became  acid,  while  the  other  did  not.  This 
remained  constant  in  a  sufficient  number  of  experiments  to 
establish  the  fact  that  the  acidity  was  due  to  the  infection. 
From  the  cultures  that  had  become  acid,  other  cultures  were 
infected,  which  also  became  acid,  thus  proving  that  the  ex- 
perimenter was  dealing  with  a  ferment  that  was  capable  of 
propagating  itself;  an  organized  ferment. 


160  THE   GERM   THEORY   OF   DISEASE. 

Microscopic  examination  showed  that  these  cultures  con- 
tained an  organism  similar  to  those  found  in  the  deeper  layers 
of  carious  dentine,  and  which  remained  constant  in  their  char- 
acters. Chemical  examination,  which  seems  to  have  been 
very  carefully  conducted,  showed  the  acid  produced  to  be 
lactic  acid.  This  acid  has  been  shown  to  be  capable  of  de- 
composing the  teeth  by  M.  Magitot  and  many  others.  Yet 
Dr.  Miller  goes  still  further,  and  by  placing  sections  of 
dentine  in  his  culture  fluids  that  he  has  infected,  finds  that 
they  are  decomposed  by  the  acid  formed ;  while  such  sections 
placed  in  such  fluids  not  infected  are  not  changed.  Thus  he 
not  only  proves  that  an  acid  is  formed,  but  that  the  acid  is 
formed  in  sufficient  amount  to  destroy  the  dentine. 

This,  when  compared  with  the  best  experimentation  previ- 
ously had,  marks  a  great  advance.  One  point  seems  to  have 
been  gained.  One  organism  has  been  traced  thus  far,  and 
may  now  be  said  to  have  been  proven  to  be  able  to  produce 
certain  of  the  phenomena  of  decay.  But  this  is  not  all. 
There  is  much  yet  to  be  done.  True,  one  other  point  is 
spoken  of  by  Dr.  Miller.  All  who  have  made  a  careful 
study  of  caries  know  that  there  is  a  peculiar  enlargement  of 
the  tubules,  which  is  not  seen  in  dentine  softened  by  acids 
alone.  Dr.  Miller  has  been  looking  for  this  also,  and  not 
without  success;  for  in  some  sections  of  dentine  exposed  to 
the  action  of  the  cultures,  he  found  the  organisms  crowding 
into  the  tubules,  and  tells  us  that  he  also  found  them  en- 
larged, as  in  natural  caries  of  the  teeth  in  the  mouth ;  indeed, 
that  he  had  before  him  veritable  caries,  artificially  produced. 

This  delineation  of  results  of  experimentation  must  have 
great  weight  in  the  settling  of  the  problems  at  issue ;  especi- 
ally if  they  are  confirmed  by  other  competent  observers. 
There  is  nothing  in  these  experiments  that  is  not  in  harmony 
with  known  facts,  unless  it  be  the  widening  of  the  tubules  by 


THE   GERM   THEORY   OP   CARIES.  161 

the  crowding  in  of  the  organisms.  It  is  known,  by  previous 
experiment,  that  this  widening  is  not  caused  by  the  lactic  acid 
as  it  exists  dissolved  in  the  surrounding  medium.  And  I  think 
very  few  will  be  willing  to  concede  that  the  organisms  can 
accomplish  this  by  physical  force.  This  point  requires  further 
investigation,  and  its  study  will  doubtless  lead  to  further  dis- 
coveries. However,  we  think  it  may  be  explained  in  advance; 
at  least,  the  effort  may  serve  to  direct  experimentation. 

In  a  previous  lecture  we  have  dwelt  at  some  length  upon 
the  digestive  fluids  of  living  organisms.  Unexpectedly  we 
find  use  for  these  ideas  now,  for  they  were  written  before  we 
saw  Dr.  Miller's  last  article.  I  have  explained  how  it  is  that 
dead  bone,  roots  of  the  temporary  teeth,  ivory  driven  into 
the  flesh,  catgut  ligatures,  sponge,  etc.,  are  dissolved  and 
removed  by  a  soluble  ferment.  I  have  also  shown  that  the 
soluble  ferment  of  the  yeast  plant  has  been  found  and  proven : 
also  that  of  ammoniacal  fermentation;  and  how  plants* take 
up  otherwise  insoluble  substances.  Now  this  widening  of  the 
tubules  is  a  conceded  fact.  It  is  also  shown  that  it  is  not 
done  by  the  lactic  acid  in  case  of  other  experiments ;  nor  can 
it  be  done  by  the  physical  force  of  the  organisms;  but  it  can, 
in  all  probability,  be  done  by  the  digestive  fluid  of  the  organ- 
ism. The  conditions  for  this  work  of  the  digestive  fluid  is 
the  same  as  that  of  the  granulations  in  widening  the  meshes 
of  the  sponge  and  finally  removing  the  last  of  it.  As  yet 
no  such  soluble  ferment  has  been  demonstrated  in  connection 
with  this  organism;  but  theoretically  it  must  exist,  and  if 
Dr.  Miller  should  undertake  to  search  for  it,  he  will  be  able 
to  demonstrate  it  speedily,  and  determine  its  co-operation  in 
producing  some  of  the  phenomena  of  decay.  At  least,  de- 
termine its  capabilities.*  This  organism  cannot  be  said  to 

*  Since  the  above  was  written  Dr.  Miller  has  also  reported  the  finding 
of  another  micro-organism  that  he  thinks  capable  of  producing  caries. 


162  THE   GERM   THEORY   OF   DISEASE. 

have  been  definitely  and  completely  studied  until  this  soluble 
ferment,  or  diastase,  be  found,  isolated,  and  its  capabilities 
separately  determined.* 

It  is  by  no  means  probable  that  this  is  the  only  organism 
that  may  stand  in  a  causative  relation  to  caries.  The  organ- 
ism of  butyric  fermentation,  possibly  that  of  acetic  fermenta- 
tion, and  a  large  number  of  others  of  the  acid  fermentations 
may  cause  decay;  nor  is  it  by  any  means  a  settled  fact  that 
decay  of  the  teeth  may  not  be  brought  about  in  part  by  other 
vital  processes  than  the  acid  fermentations.  Of  this,  how- 
ever, we  will  speak  later. 

Another  question  may  arise  in  this  matter,  and  need  ex- 
planation. I  have  repeatedly  said  that  the  waste  products 
of  an  organism  prevented  the  activity  of  that  organism,  when 
collected  in  a  certain  amount.  How,  then,  can  this  organism 
continue  to  thrive  in  its  own  waste  product,  and  thus  con- 
tinuously promote  caries  by  furnishing  more,  and  still  more, 
of  this  waste  product?  Simple  enough.  Every  chemist  who 
has  studied  lactic  fermentation  has  been  in  the  habit  of  intro- 
ducing some  form  of  lime  into  the  fermenting  fluid  to  "fix" 
the  lactic  acid  in  the  form  of  a  lactate  of  lime,  in  which  case 
it  does  not  hinder  the  progress  of  the  fermentation.  In  this 
way  a  much  larger  amount  of  the  lactic  acid  may  be  obtained, 
as  it  is  readily  regained  from  its  salts.  This  was  learned  long 
before  the  organism  was  found.  Now  in  the  production  of 
caries,  the  tooth  presents  the  lime  for  the  formation  of  the 
lactate,  and  thus  furnishes  the  very  conditions  necessary  to 
the  continuous  growth  of  the  organism. 

In  this  connection,  I  wish  to  call  attention  again  to  a  diffi- 
culty that  has  ever  existed  in  the  study  of  the  action  of 
organized  germs  in  producing  impressions  of  whatever  kind, 

*  Since  the  above  was  written  Dr.  Miller  has  reported  the  finding  of 
this  soluble  ferment. 


THE   GERM   THEORY   OF   CARIES.  163 

whether  it  be  illness  or  the  disorganization  of  structures. 
The  power  of  the  life  force  is  always  manifested  in  the  remo- 
leculization  of  matter.  The  chemical  forces  of  matter  are 
the  playthings  of  the  life  force.  The  molecule  is  compelled 
to  admit  other  elements,  is  split  in  twain,  is  torn  to  pieces  for 
the  formation  of  other  molecules  of  a  different  character ;  and 
finally,  it  is  cast  aside,  so  changed  in  its  molecular  and  physical 
characters  that  it  is  unrecognizable  as  the  same,  outside  of  the 
chemist's  laboratory.  Life  is  an  immaterial  force,  but  its 
dealings  are  with  the  material.  In  the  study  of  the  questions 
now  before  us,  it  is  with  these  remoleculizations  of  matter 
that  we  have  to  deal.  The  mere  physical  power  of  these 
low  organisms,  while  in  some  peculiar  positions  it  may 
amount  to  something,  may,  as  a  rule,  be  left  out  of  the 
count  entirely. 

If  micro-organisms  decompose  an  organic  body,  they  do  so 
by  furnishing,  through  their  remoleculizatious,  a  chemical 
substance  capable  of  acting  on  that  body.  And,  furthermore, 
this  substance  may,  and  generally  is,  produced  by  the  remo- 
leculization  of  the  elements  of  the  organic  body  being  decom- 
posed. Bacterium  lactis  lives  at  the  expense  of  starch  or 
sugar. 

If  micro-organisms  cause  an  illness,  a  fever,  or  an  inflam- 
mation, it  is  because  that  organism,  in  its  remoleculizations  of 
matter,  elaborates  a  toxic  substance  capable  of  producing 
these  results.  What  is  the  source  of  the  greater  number  of 
the  toxic  substances  known  and  used  in  the  medical  world 
to-day  ?  Take  strychnia,  opium,  quinia,  rhubarb,  aconite,  vera- 
trurn,  atropia,  nicotine,  and  a  host  of  others ;  are  they  not 
the  results  of  remoleculizations  by  the  life  force  as  manifested 
in  plants  ?  Then  take  alcohol,  ammonia,  succinic  acid,  pro- 
piouic  acid,  lactic  acid,  and  many  other  toxic  and  irritant  sub- 
stances, are  they  not  the  result  of  remoleculizations,  brought 


164  THE   GERM   THEORY   OF   DISEASE. 

about  by  the  life  force,  as  manifested  in  the  form  of  micro- 
organisms? Does  anyone  pretend  that  all  of  the  toxic  bodies 
elaborated  by  micro-organisms  have  been  found,  and  their 
effects  on  the  animal  economy  made  out?  Certainly  not. 
Then  we  may  expect  to  find  others,  if  we  make  the  search. 
It  seems  certain  that  every  organism  that  is  hurtful  to  man, 
is  so  by  the  elaboration  of  some  substance  that  has  toxic  or 
irritant  properties. 

As  we  have  said,  we  have  no  doubt  that  there  are  other 
micro-organisms  than  the  bacterium  lactis  that  may  be  instru- 
mental in  the  production  of  dental  caries.  Nor  do  we  think 
that  it  is  necessarily  only  acid-producing  organisms  that  may 
produce  caries  or  some  of  its  phenomena.  This,  however, 
need  not  be  discussed  now. 

I  wish  now  to  turn  your  attention  for  a  moment  to  another 
class  of  phenomena,  and  make  some  inquiry  into  their  possible 
participation  in  the  production  of  caries.  I  have  already 
spoken  of  the  strong  probability  that  the  otherwise  normal 
tissues,  when  under  the  influence  of  certain  qualities  of  inflam- 
mation, emit  a  fluid  of  acrid  and  very  irritating  properties. 
About  the  necks  and  other  parts  of  children  we  sometimes 
see  this  fluid  excoriating  the  skin  wherever  it  touches  it, 
seemingly  acting  the  part  of  a  caustic.  I  have  already 
referred  to  the  fact  that  dead  bone,  ivory  driven  into  the  flesh, 
sponge,  catgut  ligatures,  etc.,  are  dissolved  and  removed.  This 
causes  us  to  inquire  whether  or  not  a  substance  may  be 
elaborated  in  the  same  manner  in  the  mouth,  that  may  have 
its  quota  of  effect  in  the  production  of  the  phenomena  of 
caries. 

I  was  thoroughly  convinced  that  this  was  the  case  years 
ago,  though  I  endeavored  to  explain  the  results  by  the 
assumption  that  an  acid  was  formed.  This  is  entirely  un- 
necessary. Soluble  ferments  do  not  seem  to  depend  for  their 


THE   GERM   THEORY   OF   CARIES.  165 

action  on  either  acidity  or  alkalinity.  They  seem  to  be  con- 
trolled by  some  other  than  the  known  chemical  laws,  and 
their  action  is  not  yet  understood.  We  have  no  means  of  ex- 
plaining them.  If  a  piece  of  ivory  thrust  into  the  flesh  is 
attacked  and  burrowed  out  in  holes  by  a  secretion  thrown  out 
by  virtue  of  the  irritation  induced,  as  asserted  by  Krause, 
Kolliker  and  other  of  the  most  capable  observers  of  the 
world,  why  may  not  a  tooth  be  attacked  in  the  same  way,  by 
virtue  of  an  irritation  of  the  tissues  about  its  neck  or  during 
the  irritation  consequent  upon  its  eruption  when  this  is 
unusually  prolonged?  As  a  matter  of  fact,  it  has  been  ob- 
served that  decays  are  very  prone  to  occur  in  just  such  situa- 
tions as  tend  to  confirm  this  hypothesis.  Thirteen  years  ago 
we  drew  attention  to  this  in  a  paper  before  the  Illinois  State 
Dental  Society.  Both  before  and  since  that  time  I  have 
given  much  attention  to  this  point,  and  I  am  more  than  ever 
convinced  that  it  has  much  to  do  with  the  beginnings  of  de- 
cay. I  do  not  wish  to  be  misunderstood  in  my  view  of  this 
matter.  It  is  not  my  notion  that  decays  are  initiated  by  this 
cause  alone.  It  is  only  one  of  the  first  steps  by  which  other 
forces  which  come  later  are  rendered  operative.  The  means, 
if  you  please,  by  which  the  surface  of  the  tooth  is  first  broken, 
and  by  which  organisms  are  permitted  to  find  a  lodgment. 
Not  a  means  by  which  a  decay  is  carried  on  to  the  complete 
destruction  of  the  tooth.  This  effect  cannot  be  produced  ex- 
cept while  the  tissues  are  in  contact,  or  in  very  close  proximity 
to  the  part  in  process  of  solution,  for  the  reason  that  the 
secretion  from  the  tissues  would  be  dissipated  in  the  fluids  of 
the  mouth  before  they  could  have  time  to  produce  their 
effects  upon  the  tooth  structure. 

The  positions  at  which  these  results  are  seen  are — wisdom 
teeth,  that  come  through  very  slowly ;  on  the  buccal  surfaces 
of  the  molars  generally ;  and  sometimes  on  the  labial  surfaces 


166  THE   GEEM    THEORY   OF   DISEASE. 

of  the  upper  incisors.  In  case  of  the  wisdom  teeth,  the  fact 
that  they  are  very  often  decayed  before  they  are  fully  through 
the  gum  is  especially  remarked  ;  and  as  a  rule,  if  these  decays 
are  carefully  noted  at  a  very  early  period  of  their  progress, 
it  will  be  seen  that  they  are  different  from  other  decays  in 
several  respects.  It  always  has  its  beginning  under  the  free 
margin  of  the  gum.  There  is  usually  no  change  whatever 
in  the  appearance  of  the  tooth;  the  eye  discovers  nothing. 
The  surface  seems  normal,  or,  at  most,  the  portion  of  the 
tooth  appears  rather  whitish ;  but  on  trial  with  the  excavator 
the  instrument  will,  apparently,  break  in  through  the  enamel 
prisms,  disclosing  a  cavity  of  very  slight  depth.  It  often 
happens  that  the  enamel  may  be  easily  scraped  away  over  a 
considerable  space,  as  though  it  was  so  much  chalk.  The 
depth  will  present  much  variation ;  often  it  is  only  a  part  of 
the  thickness  of  the  enamel,  at  other  times  we  may  find  it 
extending  into  the  dentine,  in  which  it  forms  a  veritable 
cavity.  If  there  is  much  depth,  however,  the  characteristics 
will  have  assumed  the  more  usual  type. 

Occasionally  we  see  this  character  of  decay  (if  it  may  be  so 
called)  in  the  grinding  surfaces  of  the  wisdom  teeth ;  occa- 
sionally in  the  first  molar  also,  where  the  tooth  has  come 
through  very  slowly,  and  the  gum  has  been  for  a  long  time 
in  a  state  of  chronic  irritation.  It  is  characteristic  of  this 
effect  that  it  is  as  often  seen  on  the  smooth  surfaces  of  the 
teeth  as  in  the  pits  and  grooves.  No  imperfection  is  necessary 
to  prepare  the  way  for  this  manifestation. 

As  we  have  said,  this  takes  place  under  the  gum  ;  is  covered 
by  the  gum.  Now,  as  the  tooth  rises  higher  and  the  surface 
thus  affected  becomes  exposed,  these  spots  are  prone  to  become 
the  seat  of  true  caries,  with  all  of  its  usual  manifestations. 
However,  very  often  caries  does  not  take  place.  In  this  case 
a  whitish  spot  is  seen,  which  gradually  assumes  a  yellowish 


THE   GERM   THEORY   OF   CARIES.  167 

tinge,  then  brownish,  and  finally  becomes  black.  This  result 
is  brought  about  by  the  settling  into,  or  the  formation  in,  the 
affected  tissue  of  the  black  sulphurets ;  as  I  was  the  first  to 
show.  (See  Report  on  Dental  Chemistry,  by  Dr.  H.  A.  Smith, 
Transactions  of  the  American  Dental  Association,  1874, 
page  78.) 

We  see  these  spots  every  day  upon  the  sides  of  the  molars, 
in  every  stage  of  coloration,  from  ashy  white  to  a  deep  black. 
They  are  as  apt  to  be  on  the  otherwise  smooth  surfaces  as  in 
the  pits  and  grooves.  They  may  occur  on  any  of  the  teeth, 
but  are  oftenest  seen  in  the  positions  named.  -  The  decays 
that  so  often  occur  on  the  labial  surfaces  of  the  upper  in- 
cisors, are  often,  though  not  uniformly,  of  the  same  character. 

Those  decays  that  occur  just  at  the  junction  of  the  enamel 
and  cementum,  in  persons  of  middle  age  or  past,  also,  occa- 
sionally, in  younger  persons,  in  very  many  cases,  seem  to  be 
of  the  same  character.  Some  irritation  of  the  gum  at  the 
immediate  spot  seems  to  be  one  condition  of  their  beginning. 
These  also  have  some  special  characteristics  not  common  to 
other  decays.  If  they  are  closely  examined  very  early,  in 
their  inception,  it  will  be  found  that  the  cementum  has  been 
removed  and  that  the  margin  of  the  enamel  has  become 
chalky.  Soon  after  this,  if  the  case  continue  to  progress,  the 
gum,  which  till  now  was  closely  applied  to  the  part,  becomes 
everted  so  as  to  expose  the  breach  in  the  tooth.  This  often 
becomes  the  seat  of  the  most  exquisite  sensitiveness  just  at 
the  present  stage  of  the  process,  which  calls  the  attention  of 
the  patient  to  the  spot.  Generally,  however,  nothing  can  be 
seen  by  either  patient  or  operator,  except  a  slight  eversion  of 
the  gum,  and  the  slight  grooved  appearance  of  the  neck  of 
the  tooth,  which  the  operator  is  often  puzzled  to  differentiate 
from  the  normal  form  of  the  tooth.  However,  if  he  will 
carefully  press  the  gum  away  (and  he  will  find  this  abnor- 


168  THE    GERM    THEORY    OF    DISEASE. 

mally  sensitive)  until  he  can  see  the  root  of  the  tooth  below 
plainly,  it  will  be  easy  to  demonstrate  that  there  has  been  a 
decided  loss  of  substance.  Trial  with  an  instrument  will 
develop  the  fact  that  the  surface  within  this  groove  is  ex- 
ceedingly sensitive;  the  dentine  is  exposed. 

Now,  if  the  case  is  left  to  itself,  this  sensitiveness  will 
continue  for  some  weeks,  or  even  months,  and  then  abate ; 
and  it  will  be  found  that  the  case  has  taken  on  the  usual 
characters  of  decay.  It  may  cease  to  progress  and  assume 
a  dark  color,  or  it  may  progress  rapidly,  and  remain  of  a 
more  or  less  ashy  cast. 

It  has  been  our  opinion  that  this  class  of  decays,  if  that 
term  can  be  applied  at  this  stage,  is  brought  about  in  pre- 
cisely the  same  way  that  the  root  of  a  permanent  tooth  is 
partially  absorbed  on  account  of  a  chronic  irritation  of  its 
peridental  membrane.  In  other  words,  a  soluble  ferment  has 
been  called  out  by  the  irritation  that  has  dissolved  out  a  part 
of  the  tissue  at  that  point.  Or,  if  you  prefer  to  have  it  put 
in  that  way,  a  true  absorption  has  taken  place  which  forms 
the  nidus  for  the  future  decay. 

Another  class  of  decays  are  very  common,  which  I  have 
studied  very  closely,  and  which  seem  to  be  of  the  same 
character  in  their  inception.  These  begin  under  the  free 
margin  of  the  gum,  under  plates  that  abut  closely  against  the 
teeth.  These  are  usually  very  rapid  in  their  course,  evidently 
for  the  reason  that  as  soon  as  the  free  margin  of  the  gum  is 
everted,  a  pocket  is  formed  by  aid  of  the  plate,  in  which  fer- 
mentation can  proceed  to  the  very  best  advantage.  It  does 
not  seem  that  the  beginning  of  this  decay  is  often  after  the 
eversion  of  the  gum  has  uncovered  the  spot.  Of  course  we 
often  see  decays  occur  where  clasps  encircle  the  teeth  that  are 
high  up  on  the  crown.  Such  must  not  be  confounded  with 
those  that  begin  at  the  margin  of  the  cementum. 


THE   GERM   THEORY   OF   CARIES.  109 

A  question  of  great  interest  here,  and  the  findings  of  Dr. 
Miller  make  it  doubly  so,  is  the  composition  of  the  fluid  that 
is  instrumental  in  the  absorption  of  bone.  I  believe  that  I 
have  already  referred  to  the  opinion  of  Krause,  and  others 
who  regard  it  as  containing  lactic  acid  as  its  active  principle. 
Krause  bases  this  opinion  on  the  behavior  of  the  tissue  form- 
ing this  substance  toward  staining  agents.  From  his  experi- 
ments, it  seems  quite  certain  that  the  substance  has  an  acid 
reaction,  but  the  particular  acid  seems  to  me  to  be  undeter- 
mined. The  action  that  we  see  in  the  absorption  of  the  roots 
of  the  teeth  is  not  the  action  of  lactic  acid  alone.  This  acid 
dissolves  the  lime  salts  only,  leaving  the  tissues  of  the  tooth 
behind  in  the  normal  form,  as  has  been  well  shown  by  Magitot 
and  many  other  capable  experimenters. 

This,  of  course,  excludes  the  lactic  acid  as  the  exclusive 
agent  in  the  work.  Nevertheless,  the  secretion  may  contain 
this  acid  in  combination  with  some  other  active  principle. 


INDEX. 


A  PAGE 

Absorptive  digestion 82 

Absolute  demonstration  demanded 68 

Alcohol — isolation  of. 18 

early  distillation  of. 18 

Amo3boid  theory  of  contagion 57 

Antiseptics — first  explanation  of. 19 

Antiseptic  treatment  introduced  by  Mr.  Lister 41 

in  hospitals 42 

success  of. 56 

Aniline  staining .* 62 

Alkaloids— consideration  of. 118 

are  waste  products 118 

components  of  the 118 

natural  salts  of  the 126 

isolation  of  the,  necessary 127 

relation  of  the  alcohols  to  the 126 

"        of  the  organic  acids  to  the 126 

solubility  of  the... 126 

Antiphlogistics 16 

Appendix 147 

Archebiosis 35 

Astier's  discoveries 19 

Athenian  plague 12 

B 

Bacillus  Anthracis 61,  90,  127 

Bacteria — Beale's  views  of. 57 

difficulties  of  distinguishing  varieties 38 

consideration  of  the  waste  products  of. 120 

how  they  destroy  a  carcass 121 

many  of  the,  incapable  of  producing  disease 39 

regarded  as  scavengers 39 

supposition  as  to,  in  open  wounds 41 

the  accompaniments  of  disease,  not  the  cause 52 

the  active  agents  in  decompositions 41 

their  power  of  remoleculization  of  matter.... 120 

poisons  formed  by 124 

Bacterium  lactis — artificial  elimination  of  the  waste  products  of. 122 

"         in  soup 136 

termo  in  blood 84 

Bastian  on  the  origin  of  life 35 

Beale  on  disease  germs 57 

Berthelot , 84 

Black  death,  the 13 

Blood  diseases 145 

171 


172  INDEX. 

PAGE 

Caries  of  the  teeth 149 

k<      agency  of  the  soluble  ferments  in 164 

acid,  or  chemical  theory  of. 151 

"      B.  lactisin 160 

"      color  of 150,  166 

"     denned 150 

"      germ  theory  of 106 

u      origin  of  acids  supposed  to  cause 152 

widening  of  tubules  in 160 

"      vital  theory  of. 149 

Carter,  Dr.,  of  India 97 

Cells — the  relative  power  of. 114 

Cellular  digestion  in  the  higher  animals 98 

Century— the  19th 17 

Changes  in  the  products  of  micro-organisms 134 

Chemical  changes  ia  putrefaction — Gradle 130 

Cohn's  classification  of  micro-organisms 40 

Contagion — amoeboid  theory  of. 57 

Beale's  views  of 57 

first  notions  of. 12 

modes  of  communication , 73 

origin  of. 59 

not  a  fermentation 57 

Cotton  as  an  air  filter 28 

Cultures — dry  slide 66 

fluid  employed  by  Pasteur 33 

inoculations  made  from  pure 67 

"          objections  to  flask 66 

D 

Diastase 92 

"       effects  of,  on  starch 92 

Decomposition — agents  of. 32 

Decompositions,  contagions  and  miasms  of  the   same   class  as  the 

fermentations 38 

Denovo — origin  of  life 35 

Difficulties  of  the  germ  theory 27,  38 

Discovery  of  the  yeast  plant 20 

Digestion — absorptive  and  resorptive 82 

by  the  yeast  plait 84 

by  the  germs  of  seeds 91 

by  the  germs  of  tubers 92 

by  the  higher  plants 89 

by  the  micrococcus  urea 89 

cellular,  in  the  higher  animals 98 

extraneous  to  the  body 82 

example  of  without  a  stomach 84 

experiments  by  Sachs 90 

of  blood  clot 100 

"           "    ivory 105 


INDEX.  173 

PAGE 

Digestion  of  ligatures 101 

"    necrosed  bone 104 

"    solid  food  by  bacteria 86 

"    sponge  in  the  sponge  graft 102 

"    the  roots  of  the  milk  teeth 99 

primary 82 

propositions  relating  to 81 

type  of,  in  unicellular  plants  and  animals 85 

Direct  examination  for  microscopic  organisms 44 

Disease  Germs — Beale's  views  of. 57 

relation  of  the  white  corpuscles  to 58 


E 

Early  discoveries 18 

Effect  of  plagues  on  civilization 13 

Schwan's  discoveries 21 

"      Schroeder's  discoveries 41 

Evidence — nature  of. 43 

fractional 45 

unsatisfactory 45 

Excretion  in  plants 117 

by  roots  of  plants 117 

by  seeds  in  sprouting 117 

"         manner  of,  in  plants 119 

Explanatory 42 

Extreme  views ,     56 


F 

Fabroni 19 

Fermentation — bladder  experiment 19 

compared  with  contagion 17 

compared  with  vaccine ." 17 

different  from  chemical  action 19 

early  notions  of. 15 

early  explanations  of 16 

filtering  paper  experiments 19 

hypothesis 15 

Ferments— gaseous 23 

gaseous,  disproved 29 

soluble.. 82,  106 

in  the  changes  of  the  form  of  bone 108 

"      relation  of  to  living  tissues 108 

"      pathological  formation  of. 106,108 

relation  to  decay  of  the  teeth 106 

"      tissue  changes  for  forming 108 

First  traces 12 

"     definite  announcement  of  the  germ  theory 14 

Fixed  material 119 

Formed  material .  119 


174  INDEX. 


PAGE 


Gangrene  in  mice  ........  ........................................................  63,  127 

Gay-Lussac's  experiments  .........................................................     18 

Germs—  effect  of  heat  upon  ....................................................  29,  33 

'*        numbers  of  in  the  air  ....................................................     33 

Germ  theory—  first  announcement  of  the  modern  ...........................     20 

Gradle  —  chemical  changes  in  putrefaction  ..............................  130,  143 

H 

Hirschfield  .........................................  .........  .  ...........................  44 

Historical  ................................................................................  11 

Hospitals  —  antiseptic  treatment  in  ...............................................  42 

"  infection  experiment  in  .............................................  53 

"  supposed  infection  of  ........................  ,  .......................  42 

I 

Incentives  to  the  study  of  contagions  ...........................................  13 

Infection  experiments  ..........................................................  .  ____  47 

"         of  rabbits  ..................................................................  47 

a         successful,  by  Davaine  .................................................  48 

u         with  filtered  fluids  .......................................................  48 

Inflammations—  relations  of  micro-organisms  to  ............................  143 

Introduction*  ..........................................................................  11 

Jenner's  discovery  of  vaccine  .....................................................     16 

K 
Klebs  ...............................................................................  54,  130 

k       on  spontaneous  generation  ................................................     54 

'       basis  of  future  inquiry  ......................................................     55 

Koch—  a  distinctive  feature  developed  by  ......................................     65 

experiments  of.  ....................................  «  .........................     62 

gangrene  induced  by  ..................................................  63,  127 

his  experiments  with  mice  ................................................     63 

his  plan  of  staining  .........................................................     62 

poisoning  with  septic  matter  .............................................  128 

Krause  on  the  osteoclasts  ...........................................................  105 

L 
Latour  and  Schwan  ..................................................................     20 

Law  of  the  formation  of  the  waste  products  .................................   113 

Lecture  1st  ..............................................................................     11 

"       2d  ..............................................................................     35 

"       3d  ..............................................................................     57 

"       4th  ..............................................................................     79 

"       5th  ..............................................................................     96 

"       6th  ..............................................................................  Ill 

"       7th  ..............................................................................    T'O 

"       8th  .......................................................................  .....  149 

Leuwenhceck  discovers  the  spermatozoa  .......................................     14 

Leuwenhceck's  microscopic  discoveries  .......................................     1'J 


INDEX.  175 

PAGE 

Lieber  and  Rottenstein  on  caries 153 

Liebig's  law  of  the  fermentations 113 

molecular  motion  theory  still  claimed 62 

"        explanation  of  susceptibility.  24 

14        basis  for  the  recognition  of  life 26 

"        explanation  of  fermentation 21 

of  the  formation  of  yeast 22 

"                 u              "       action  of  medicines 22 

of  contagions -. 23 

of  miasms 23 

"        opposition  to  the  germ  theory 21 

"        recognition  of  gaseous  ferments 23 

Liebig  on  the  destruction  of  poisons  in  the  stomach 25 

"         "       vitality  of  contagions 24 

"     on  excretion  by  plants 117 

Life— de  novo  origin  of. 35 

"      how  supported 112 

"      nature  of. 125,  163 

Lifter's  antiseptic  treatment 41 

"      experiments  with  B.  Termo 50,  85 

"       reply 56 

Logical  sequence 38 

M 

Magitot  on  caries  of  the  teeth 155 

Malarious  fevers  caused  by  germs 14 

Manner  in  which  micro-organisms  act  in  producing  disease 136 

Miasmatic  contagion 46 

Miasms  and  contagions 45 

"        Liebig's  explanation  of. 23 

Micro-organisms — classification  of 40 

changes  in  the  products  of. 135 

dilution  of. 51 

destroyed  by  decomposition 70 

destroyed  by  drying ,  73 

destroyed  by  the  tissues 142 

effects  of  physical  presence  of 146 

first  demonstration  of,  in  diseased  tissues 44 

first  demonstration  of,  in  blood 44 

first  recognition  of  particular  forms  of,  in  connec- 
tion with  particular  forms  of  disease 45 

forms  of 40 

harmless  varieties  of. 69 

isolation  of  pathogenic 68 

modes  of  propagation 40 

matter  secreted  by 64 

non-pathogenic  and  pathogenic 79 

no  suppuration  without 55 

not  found  in  normal  tissues 63 

not  the  cause  of  all  disease 146 

per  se,  not  a  sufficient  cause  of  disease 80 


176  INDEX. 

PAGE 

Micro-organisms — presence  of,  in  healthy  tissues 52 

possible  morphological  differences  in 55 

pathogenic,  now  demonstrated 68 

relation  of,  to  disease  processes 53 

"       to  inflammation 143 

"       to  pus  formation 143 

relation  of  leucocytes  to : 141,  142 

resistance  of  the  tissues  to 138 

**                      virulent,  action  of. 53 

varieties  in  power  of  disease-producing 71 

Miller's  experiments 158 

"             u           with  B.  Lactis  in  soup 136 

Miller  on  caries  of  the  teeth 158 

Molecular  motion  theory 22 

M.  Musculus 89 

N 

Nature  of  the  evidence 43 

Necrosed  bone 104 

Needham  and  Spalanzani 30 

New  functions  apparent  only 114 

Nineteenth  century 17 

Nutrition 94 

O 

Office  of  micro-organisms 123 

Opinion  of  Lister 56 

"     Thiersch 49,  53 

Osteoclasts 108 

Oxamide-oxalic  acid  experiment 27 

Oxygen — proof  that  it  is  not  the  active  agent  in  decomposition 20,  41 

P 

Parasites 110 

Pasteur 30 

11         conclusions  of 34 

"         cultivation  fluids  employed  by 33 

u         effects  of  his  work 34 

11         flask  cultivations  by 30 

u         isolates  various  ferments 32 

u         one  point  of  failure  in  the  experiments  of 33 

Pathogenic  organisms  demonstrated 68 

Pathological  formation  of  ferments 106 

Phlogiston 15 

Physiological  changes  in  cells 59 

Plants — digestion  by 89 

Poison  destroyed  by  bacteria 131 

u      formation  of  by  bacteria 127 

a       from  bacteria — Panum 131 

"      produced  by  micrococci 64 

Poisoning  different  from  infection 129,  133,  151 

Poisons — action  of  explained  by  Liebig 23 


INDEX.  177 

PAGE 

Poisons — destroyed  in  the  stomach 25 

how  affected  by  temperature 25 

not  always  found  in  putrefaction,  and  why 132 

not  destroyed  in  the  stomach 25 

result  from  micro-organisms 124 

Propositions  relating  to  digestion 81 

Ptomains 131 

Pure  virus  necessary  for  inoculations 65 

Putrefaction — early  examination  of. 18 

organisms  necessary  to 20 

explained  by  Liebig 22 

Pyaemia — production  of. 48 

R 

Rabbits — infection  of. 47 

Recklinghausen 44 

Regnault  on  diastase 92 

Relapsing  fever 97 

Remoleculize — definition  of 83 

Resorptive  digestion 98 

Resorption  of  the  roots  of  the  milk  teeth 99 

Rust  on  wheat 46 

S 

Sachs— experiments  by 90,  239 

Salmon,  Dr.  E.  D 51,  73 

Schroeder 28 

Schwan 20 

Seeds — sameness  in  physiology  of. 114 

11        sprouting  of. 91 

"        varieties  in  the  form  of. Ii4 

Sepsin  and  sulphate  of  atropia 143 

Sepsis — poison  of. 127,  129 

Septicaemia  and  pyaemia 65 

bacillus  of. 64 

field  mice  insusceptible  to 65 

in  mice 63,  129 

Soluble  ferment 82 

dissolving  power  of  the 106 

"              of  B.  Lactis 162 

"  B.  Termo 89 

"  micrococcus  urea 86 

11  the  yeast  plant 84 

Spallanzani  and  Needham 30 

Spermatozoa  discovered 14 

Sponge  grafts 102 

Spontaneous  generation 20,  54 

Spores  and  habits  of  micro-organisms 72 

Spore  formation 72 

Stahl 15 

StahPs  conclusion  in  regard  to  fermentation  and  decomposition 18 

Staining  micro-organisms 62 

Sternberg  on  poisons  evolved  by  micro-organisms 130 


178  INDEX. 

PAGE 

Sternberg  on  the  relation  of  leucocytes  to  micro-organisms 140 

Summary  of  history 74 

Susceptibility — Liebig's  explanation  of. 24 

Sydenham 15 

T 

The  evidence 69 

Theory  of  molecular  motion 22 

Thiersch 49 

Thiersch's  infection  experiment 53 

Toricellean  vacuum  and  fermentation 18 

U 

Urea  an  alkaloid 116 

Uredo 46 

Urine — changes  in  the 115 

Utilizing  discoveries , 41 

V 

Vaccine — discovery  of. 16 

"          experiments  with 16 

Varro 14 

Vegetable  world  divided  into  two  classes 122 

Vibrios 32 

Views  of  representative  men 48-56 

Virchow 53 

Volkman 55 

W 
Waldeyer 44 

Walnut  trees  injurious  to  other  vegetation 118 

Waste  products — 6th lecture Ill 

abundance  of,  from  micro-organisms 120)  127 

artificial  elimination  of,  in  B.  Lactis 122 

as  medicines 120 

"  divided  into  two  classes 113,115 

effects  of,  on  life 94 

how  formed 123 

necessary  to  life 112 

"  not  yet  sufficiently  studied 124 

of  plants 117 

poisonous 116 

respiratory 117 

"  Schwan  and  Liebig  on Ill 

11  tabulated  list  of 123 

"  the  laws  of. 112 

"  urinary 117,  124 

Watt  on  caries  of  the  teeth 155 

Y 

Yeast  plant 96 

digestion  by  the 84 

Z 

Zymosis 15 


CATALOGUE  No.  7. 


OCTOBER,  1890. 


A  CATALOGUE 

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INCLUDING  THE 


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Or  the  Chemistry  of  the  Carbon  Compounds.  By  Prof. 
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literature,  it  is  refreshing  to  meet  with  an  author  who  knows  both 
what  to  say  and  when  he  has  said  it.  The  work  of  Dr.  Goodhart 
(admirably  conformed,  by  Dr.  Starr,  to  meet  American  require- 
ments) is  the  nearest  approach  to  clinical  teaching  without  the 
actual  presence  of  clinical  material  that  we  have  yet  seen." — New 
York  Medical  Record. 

No.  7.    PRACTICAL  THERAPEUTICS. 

FOURTH  EDITION,  WITH  AN  INDEX  OF  DISEASES. 

Practical  Therapeutics,  considered  with  reference  to 
Articles  of  the  Materia  Medica.  Containing,  also,  an 
Index  of  Diseases,  with  a  list  of  the  Medicines 
applicable  as  Remedies.  By  EDWARD  JOHN  WARING, 
M.D.,  F.R.C.P.  Fourth  Edition.  Rewritten  and  Re- 
vised by  DUDLEY  W.  BUXTON,  M.D.,  Asst.  to  the  Prof, 
of  Medicine  at  University  College  Hospital. 

"  We  wish  a  copy  could  be  put  in  the  hands  of  every  Student  or 
Practitioner  in  the  country.  In  our  estimation,  it  is  the  best  book 
of  the  kind  ever  written.  — N.  Y.  Medical  Journal. 

No.  8.    MEDICAL  JURISPRUDENCE  AND 
TOXICOLOGY. 

NEW,  REVISED  AND  ENLARGED  EDITION. 

By  John  J.  Reese,  M.D.,  Professor  of  Medical  Jurispru- 
dence and  Toxicology  in  the  University  of  Pennsyl- 
vania ;  President  of  the  Medical  Jurisprudence  Society 
of  Phila. ;  2d  Edition,  Revised  and  Enlarged. 

"  This  admirable  text-book." — Amer.Jour.  of  Med.  Sciences. 

"  We  lay  this  volume  aside,  after  a  careful  perusal  of  its  pages, 
with  the  profound  impression  that  it  should  be  in  the  hands  of  every 

doctor  and  lawyer.  It  fully  meets  the  wants  of  all  students 

He  has  succeeded  in  admirably  condensing  into  a  handy  volume  all 
the  essential  points."— Cincinnati  Lancet  and  Clinic. 

Price  of  each  Book,  Cloth,  $3,00 ;  Leather,  $3.50. 


6          STUDENTS'  TEXT-BOOKS  AND  MANUALS. 

ANATOMY. 

Macalister's  Human  Anatomy.  816  Illustrations.  A  new 
Text-book  for  Students  and  Practitioners,  Systematic  and  Topo- 
graphical, including  the  Embryology,  Histology  and  Morphology 
of  Man.  With  special  reference  to  the  requirements  of 
Practical  Surgery  and  Medicine.  With  816  Illustrations, 
400  of  which  are  original.  Octavo.  Cloth,  7.50;  Leather,  8.50 
Ballou's  Veterinary  Anatomy  and  Physiology.  Illustrated. 
By  Wm.  R.  Ballou,  M.D.,  Professor  of  Equine  Anatomy  at  New 
York  College  of  Veterinary  Surgeons.  29  graphic  Illustrations. 
I2mo.  Cloth,  i. oo ;  Interleaved  for  notes,  1.25 

Holden's  Anatomy.  A  manual  of  Dissection  of  the  Human 
Body.  Fifth  Edition.  Enlarged,  with  Marginal  References  and 
over  200  Illustrations.  Octavo.  Cloth,  5.00;  Leather,  6.00 

Bound  in  Oilcloth,  for  the  Dissecting  Room,  $4.50. 
"  No  student  of  Anatomy  can  take  up  this  book  without  being 
pleased  and  instructed.  Its  Diagrams  are  original,  striking  and 
suggestive,  giving  more  at  a  glance  than  pages  of  text  description. 
*  *  *  The  text  matches  the  illustrations  in  directness  of  prac- 
tical application  and  clearness  of  detail." — New  York  Medical 
Record. 

Holden's  Human  Osteology.    Comprising  a  Description  of  the 
Bones,  with  Colored  Delineations  of  the  Attachments   of  the 
Muscles.     The  General  and  Microscopical  Structure  of  Bone  and 
its  Development.    With  Lithographic  Plates  and  Numerous  Illus- 
trations.    Seventh  Edition.     8vo.  Cloth,  6.00 
Holden's  Landmarks,  Medical  and  Surgical.   4th  ed.   Clo.,  1.25 
Heath's  Practical  Anatomy.    Sixth  London  Edition.    24  Col- 
ored Plates,  and  nearly  300  other  Illustrations.  Cloth,  5.00 
Potter's  Compend  of  Anatomy.     Fifth  Edition.     Enlarged. 
16  Lithographic  Plates.     117  Illustrations. 

Cloth,  i.oo;  Interleaved  for  Notes,  1.25 

CHEMISTRY. 

Hartley's  Medical  Chemistry.  Second  Edition.  A  text-book 
prepared  specially  for  Medical,  Pharmaceutical  and  Dental  Stu- 
dents. With  50  Illustrations,  Plate  of  Absorption  Spectra  and 
Glossary  of  Chemical  Terms.  Revised  and  Enlarged.  Cloth,  2. 50 

Trimble.  Practical  and  Analytical  Chemistry.  A  Course  in 
Chemical  Analysis,  by  Henry  Trimble,  Prof,  of  Analytical  Chem- 
istry in  the  Phila.  College  of  .Pharmacy.  Illustrated.  Third 
Edition.  8vo.  Cloth,  1.50 

iff"  See  pages  2  to  5  for  list  of  Students'  Manuals. 


STUDENTS'  TEXT-BOOKS  AND  MANUALS.         T 

Chemistry  : — Continued. 

Bloxatn's  Chemistry,  Inorganic  and  Organic,  with  Experiments. 
Seventh  Edition.  Enlarged  and  Rewritten.  330  Illustrations. 

Cloth,  4.50;  Leather,  5.50 

Richter's  Inorganic  Chemistry.  A  text-book  for  Students. 
Third  American,  from  Fifth  German  Edition.  Translated  by 
Prof.  Edgar  F.  Smith,  PH.D.  89  Wood  Engravings  and  Colored 
Plate  of  Spectra.  Cloth,  2.00 

Richter's  Organic  Chemistry,  or  Chemistry  of  the  Carbon 
Compounds.  Illustrated.  Cloth,  3.00  ;  Leather,  3.50 

Symonds.  Manual  of  Chemistry,  for  the  special  use  of  Medi- 
cal Students.  By  BKANDRETH  SYMONDS,  A.M.,  M.D.,  Asst. 
Physician  Roosevelt  Hospital,  Out- Patient  Department;  Attend- 
ing Physician  Northwestern  Dispensary,  New  York.  lamo. 

Cloth,  2.00 ;  Interleaved  for  Notes,  2.40 

Tidy.     Modern  Chemistry.    2d  Ed.  Cloth,  5.50 

Leffmann's  Compend  of  Chemistry.  Inorganic  and  Organic. 
Including  Urinary  Analysis.  Third  Edition.  Revised. 

Cloth,  i.oo;   Interleaved  for  Notes,  1.25 

Leffmann  and  Beam.  Progressive  Exercises  in  Practical 
Chemistry.  i2mo.  Illustrated.  Cloth,  i.oo 

Muter.  Practical  and  Analytical  Chemistry.  Second  Edi- 
tion. Revised  and  Illustrated.  Cloth,  2.00 

Holland.  The  Urine,  Common  Poisons,  and  Milk  Analysis, 
Chemical  and  Microscopical.  For  Laboratory  Use.  3d 
Edition,  Enlarged.  Illustrated.  Cloth,  i.oo 

Van  Niiys.     Urine  Analysis.     Illus.  Cloth,  2.00 

Wolff's  Applied  Medical  Chemistry.  By  Lawrence  Wolff, 
M.D.,Dem.  of  Chemistry  in  Jefferson  Medical  College.  Clo.,i.oo 

CHILDREN. 

Goodhart  and  Starr.  The  Diseases  of  Children.  Second 
Edition.  By  J.  F.  Goodhart,  M.D.,  Physician  to  the  Evelina 
Hospital  for  Children;  Assistant  Physician  to  Guy's  Hospital, 
London.  Revised  and  Edited  by  Louis  Starr,  M.D.,  Clinical 
Professor  of  Diseases  of  Children  in  the  Hospital  of  the  Univer- 
sity of  Pennsylvania;  Physician  to  the  Children's  Hospital, 
Philadelphia.  Containing  many  Prescriptions  and  Formulae, 
conforming  to  the  U.  S.  Pharmacopoeia,  Directions  for  making 
Artificial  Human  Milk,  for  the  Artificial  Digestion  of  Milk,  etc. 
Illustrated.  Cloth,  3.00;  Leather,  3.50 

Hatfield.  Diseases  of  Children.  By  M.  P.  Hatfield,  M.D.  , 
Professor  of  Diseases  of  Children,  Chicago  Medical  College. 
i2mo.  Cloth,  i.oo;  Interleaved,  1.25 

Day.  On  Children.  A  Practical  and  Systematic  Treatise. 
Second  Edition.  8vo.  752  pages.  Cloth,  3.00;  Leather,  4.00 
ee  pages  14  and  /jr  for  list  of  f  Quiz-  Compends  ? 


8          STUDENTS'  TEXT-BOOKS  AND  MANUALS. 

Children:—  Continued. 

Meigs  and  Pepper.  The  Diseases  of  Children.  Seventh 
Edition.  8vo.  Cloth,  5.00;  Leather,  6.00 

Starr.  Diseases  of  the  Digestive  Organs  in  Infancy  and 
Childhood.  With  chapters  on  the  Investigation  of  Disease, 
and  on  the  General  Management  of  Children.  By  Louis  Starr, 
M.D.,  Clinical  Professor  of  Diseases  of  Children  in  the  Univer- 
sity of  Pennsylvania.  Illus.  %  Cloth,  2.50 

DENTISTRY. 

Fillebrown.     Operative  Dentistry.    330  Illus.          Cloth,  2.50 
Flagg's  Plastics  and  Plastic  Filling,     sd  Ed.         Preparing. 
Gorgas.     Dental  Medicine.    A  Manual  of  Materia  Medica  and 
Therapeutics.     Third  Edition.  Cloth,  3.50 

Harris.  Principles  and  Practice  of  Dentistry.  Including 
Anatomy,  Physiology,  Pathology,  Therapeutics,  Dental  Surgery 
and  Mechanism.  Twelfth  Edition.  Revised  and  enlarged  by 
Professor  Gorgas.  1028  Illustrations.  Cloth,  7.00  ;  Leather,  8.00 
Richardson's  Mechanical  Dentistry.  Fifth  Edition.  569 
Illustrations.  8vo.  Cloth,  4.50;  Leather,  5.50 

Sewill.     Dental  Surgery.    200  Illustrations,     sd  Ed.   Clo.,  3.00 
Stocken's  Dental  Materia  Medica.  Third  Edition.  Cloth,  2.50 
Taft's  Operative  Dentistry.    Dental  Students  and  Practitioners. 
Fourth  Edition.     100  Illustrations.        Cloth,  4.25  ;  Leather,  5.00 
Talbot.     Irregularities  of  the  Teeth,  and  their  Treatment. 
Illustrated.     8vo.     Second  Edition.  Cloth,  3.00 

Tomes'  Dental  Anatomy.     Third  Ed.     191  Illus.      Cloth,  4.00 
Tomes'  Dental   Surgery,      sd  Edition.      Revised.      292  Illus. 
772  Pages.  Cloth,  5.00 

Warren.  Compend  of  Dental  Pathology  and  Dental  Medi- 
cine. Illustrated.  Cloth,  i.oo;  Interleaved,  1.25 

DICTIONARIES. 

Gould's  New  Medical  Dictionary.  Containing  the  Definition 
and  Pronunciation  of  all  words  in  Medicine,  with  many  useful 
Tables  etc.  %  Dark  Leather,  3.25  ;  %  Mor.,  Thumb  Index  4.23 

Cleaveland's  Pronouncing  Pocket  Medical  Lexicon,  sist 
Edition.  Giving  correct  Pronunciation  and  Definition.  Very 
small  pocket  size.  Cloth,  red  edges  .75  ;  pocket-book  style,  i.oo 

Ixmgley •  s  Pocket  Dictionary.  The  Student's  Medical  Lexicon, 
giving  Definition  and  Pronunciation  of  all  Terms  used  in  Medi- 
cine, with  an  Appendix  giving  Poisons  and  Their  Antidotes, 
Abbreviations  used  in  Prescriptions,  Metric  Scale  of  Doses,  etc. 
24mo.  Cloth,  i.oo;  pocket-book  style,  1.25 

J8ST" Seepages  2  to  5  for  list  of  Students'  Manuals. 


STUDENTS'  TEXT-BOOKS  AND  MANUALS.          9 

EYE. 

Arlt.  Diseases  of  the  Eye.  Including  those  of  the  Conjunc- 
tiva, Cornea,  Sclerotic,  Iris  and  Ciliary  Body.  By  Prof.  Von 
Arlt.  Translated  by  Dr.  Lyman  Ware.  Illus.  8vo.  Cloth,  2.50 

Hartridge  on  Refraction.    4th  Ed.  Cloth,  2.00 

Meyer.  Diseases  of  the  Eye.  A  complete  Manual  for  Stu- 
dents and  Physicians.  270  Illustrations  and  two  Colored  Plates. 
8vo.  Cloth,  4.50;  Leather,  5.50 

Fox  and  Gould.  Compend  of  Diseases  of  the  Eye  and 
Refraction.  2d  Ed.  Enlarged.  71  Illus.  39  Formulae. 

Cloth,  i. oo  ;  Interleaved  for  Notes,  1.25 

ELECTRICITY. 

Mason's  Compend  of  Medical  and  Surgical   Electricity. 

With  numerous  Illustrations.     i2mo.  Cloth,  i.oo 

HYGIENE. 

Parkes'  (Ed.  A.)  Practical  Hygiene.  Seventh  Edition,  en- 
larged. Illustrated.  8vo.  Cloth,  4.50 

Parkes'  (L.  C.)  Manual  of  Hygiene  and  Public  Health. 
i2jno.  Cloth,  2.50 

Wilson's  Handbook  of  Hygiene  and  Sanitary  Science. 
Sixth  Edition.  Revised  and  Illustrated.  Cloth,  2.75 

MATERIA  MEDICA  AND  THERAPEUTICS. 

Potter's  Compend  of  Materia  Medica,  Therapeutics  and 

Prescription  Writing.     Fifth  Edition,  revised  and  improved. 

Cloth,  i.oo;  Interleaved  for  Notes,  1.25 

Biddle's  Materia  Medica.  Eleventh  Edition.  By  the  late 
John  B.  Biddle,  M.D.,  Professor  of  Materia  Medica  in  Jefferson 
Medical  College,  Philadelphia.  Revised,  and  rewritten,  by 
Clement  Biddle,  M.D.,  Assist.  Surgeon,  U.  S.  N.,  assisted  by 
Henry  Morris,  M.D.  8vo.,  illustrated.  Cloth,  4.25;  Leather,  5.00 

Headland's  Action  of  Medicines,    gih  Ed.    8vo.      Cloth,  3.00 

Potter.  Materia  Medica,  Pharmacy  and  Therapeutics. 
Including  Action  of  Medicines,  Special  Therapeutics,  Pharma- 
cology, etc.  Second  Edition.  Cloth,  4.00 ;  Leather,  5,00 

Starr,  Walker  and  Powell.  Synopsis  of  Physiological 
Action  of  Medicines, based  upon  Prof.  H.  C.  Wood's  "  Materia 
Medica  and  Therapeutics."  3d  Ed.  Enlarged.  Cloth,  .75 

Waring.  Therapeutics.  With  an  Index  of  Diseases  and 
Remedies.  4th  Edition.  Revised.  Cloth,  3.00;  Leather,  3.50 
.*3~  See  pages  14  and  /j  for  list  of  f  Quiz- Commends  f 


10        STUDENTS'  TEXT-BOOKS  AND  MANUALS. 

MEDICAL  JURISPRUDENCE. 

Reese.  A  Text-book  of  Medical  Jurisprudence  and  Toxi- 
cology. By  John  J.  Reese,  M.D.,  Professor  of  Medical  Juris- 
prudence and  Toxicology  in  the  Medical  Department  of  the 
University  of  Pennsylvania ;  President  of  the  Medical  Juris- 
prudence Society  of  Philadelphia;  Physician  to  St.  Joseph's 
Hospital ;  Corresponding  Member  of  The  New  York  Medico- 
legal  Society,  sd  Edition.  Cloth,  3.00;  Leather,  3.50 

Woodman  and  Tidy's  Medical  Jurisprudence  and  Toxi- 
cology. Chromo-Lithographic  Plates  and  116  Wood  engravings. 

Cloth,  7.50;  Leather,  8.50 

OBSTETRICS  AND  GYNAECOLOGY. 

Byford.  Diseases  of  Women.  The  Practice  of  Medicine  and 
Surgery,  as  applied  to  the  Diseases  and  Accidents  Incident  to 
Women.  By  W.  H.  Byford,  A.M.,  M.D.,  Professor  of  Gynaecology 
in  Rush  Medical  College  and  of  Obstetrics  in  the  Woman's  Med- 
ical College,  etc.,  and  Henry  T.  Byford,  M.D.,  Surgeon  to  the 
Woman's  Hospital  of  Chicago  ;  Gynaecologist  to  St.  Luke's 
Hospital,  etc.  Fourth  Edition.  Revised,  Rewritten  and  En- 
larged. With  306  Illustrations,  over  100  of  which  are  original. 
Octavo.  832  pages.  Cloth,  5.00  ;  Leather,  6.00 

Cazeaux  and  Tarnier's  Midwifery.  "With  Appendix,  by 
Munde.  The  Theory  and  Practice  of  Obstetrics  ;  including  the 
Diseases  of  Pregnancy  and  Parturition,  Obstetrical  Operations, 
etc.  By  P.  Cazeaux.  Remodeled  and  rearranged,  with  revi- 
sions and  additions,  by  S.  Tarnier,  M.D.,  Professor  of  Obstetrics 
and  Diseases  of  Women  and  Children  in  the  Faculty  of  Medicine 
of  Paris.  Eighth  American,  from  the  Eighth  French  and  First 
Italian  Edition.  Edited  by  Robert  J.  Hess,  M.D.,  Physician  to 
the  Northern  Dispensary,  Philadelphia,  with  an  appendix  by 
Paul  F.  Munde,  M.D.,  Professor  of  Gynaecology  at  the  N.  Y. 
Polyclinic.  Illustrated  by  Chromo- Lithographs,  Lithographs, 
and  other  Full-page  Plates,  seven  of  which  are  beautifully  colored, 
and  numerous  Wood  Engravings.  Students'  Edition.  One 
Vol.,8vo.  Cloth,  5.00;  Leather,  6.00 

Lewers'  Diseases  of  Women.  A  Practical  Text-Book.  139 
Illustrations.  Second  Edition.  Cloth,  2.50 

Parvin's  Winckel's  Diseases  of  Women.  Second  Edition. 
Including  a  Section  on  Diseases  of  the  Bladder  and  Urethra. 
150  Illus.  Revised.  Seepages.  Cloth,  3.00;  Leather,  3.50 

Morris.    Compend  of  Gynaecology.     Illustrated.      Cloth,  i.oo 

Winckel's  Obstetrics.  A  Text-book  on  Midwifery,  includ- 
ing the  Diseases  of  Childbed.  By  Dr.  F.  Winckel,  Professor 
of  Gynaecology,  and  Director  of  the  Royal  University  Clinic  for 
Women,  in  Munich.  Authorized  Translation,  by  J.  Clifton 
Edgar,  M.D.,  Lecturer  on  Obstetrics,  University  Medical  Col- 
lege, New  York,  with  nearly  200  handsome  illustrations,  the 
majority  of  which  are  original  with  this  work.  Octavo. 

Cloth,  6.00  ;   Leather,  7.00 

Landis'  Compend  of  Obstetrics.  Illustrated.  4th  edition, 
enlarged.  Cloth,  i.oo;  Interleaved  for  Notes,  1.25 

e  pages  2  to  3  for  list  of  New  Manuals. 


STUDENTS'   TEXT-BOOKS  AND  MANUALS.         11 

Obstetrics  and  Gynaecology  : —  Continued. 

Galabin's  Midwifery.  By  A.  Lewis  Galabin,  M.D.,  F.R.C.P. 
227  Illustrations.  See  page  3.  Cloth,  3.00;  Leather,  3.50 

Glisan's  Modern  Midwifery.    2d  Edition.  Cloth,  3.00 

Rigby's  Obstetric  Memoranda.    4th  Edition.  Cloth,  .50 

Meadows'  Manual  of   Midwifery.     Including  the  Signs  and 

Symptoms  of  Pregnancy,  Obstetric  Operations,  Diseases  of  the 

Puerperal  State,  etc.     145  Illustrations.     494  pages.    Cloth,  2.00 

Swayne's  Obstetric  Aphorisms.      For  the  use  of  Students 

commencing  Midwifery  Practice.     8th  Ed.     i2mo.       Cloth,  1.25 

PATHOLOGY.    HISTOLOGY.    BIOLOGY. 

Bowlby.  Surgical  Pathology  and  Morbid  Anatomy,  for 
Students.  135  Illustrations.  i2mo.  Cloth,  2.00 

Davis'  Elementary  Biology.     Illustrated.  Cloth,  4.00 

Gilliam's  Essentials  of  Pathology.  A  Handbook  for  Students. 
47  Illustrations.  i2mo.  Cloth,  2.00 

*+*The  object  of  this  book  is  to  unfold  to  the  beginner  the  funda- 
mentals of  pathology  in  a  plain,  practical  way,  and  by  bringing 
them  within  easy  comprehension  to  increase  his  interest  in  the  study 
of  the  subject. 

Gibbes'  Practical  Histology  and  Pathology.    Third  Edition. 

Enlarged.     i2mo.  Cloth,  1.75 

Virchow's  Post-Mortem  Examinations.    2d  Ed.    Cloth,  i.oo 

PHYSIOLOGY. 

Yeo's  Physiology.  Fourth  Edition.  The  most  Popular  Stu- 
dents' Book.  By  Gerald  F.  Yeo,  M.D.,  F.R.C.S.,  Professor  of 

'  Physiology  in  King's  College,  London.  Small  Octavo.  758 
pages.  321  carefully  printed  Illustrations.  With  a  Full 
Glossary  and  Index.  See  Page  3.  Cloth,  3.00;  Leather,  3.50 

Brubaker's  Compend  of  Physiology.  Illustrated.  Fifth 
Edition.  Cloth,  i.oo;  Interleaved  for  Notes,  1.25 

Stirling.  Practical  Physiology,  including  Chemical  and  Ex- 
perimental Physiology.  142  Illustrations.  Cloth,  2.25 

Kirke's  Physiology.  New  i2th  Ed.  Thoroughly  Revised  and 
Enlarged.  502  Illustrations.  Cloth,  4.00;  Leather,  5.00 

Landois'  Human  Physiology.  Including  Histology  and  Micro- 
scopical Anatomy,  and  with  special  reference  to  Practical  Medi- 
cine. Third  Edition.  Translated  and  Edited  by  Prof.  Stirling. 
692  Illustrations.  Cloth,  6.50;  Leather,  7.50 

"  With  this  Text-book  at  his  command,  no  student  could  fail  in 

his  examination." — Lancet. 

Sanderson's  Physiological  Laboratory.  Being  Practical  Ex- 
ercises for  the  Student.  350  Illustrations.  8vo.  Cloth,  5.00 

Tyson's  Cell  Doctrine.  Its  History  and  Present  State.  Illus- 
trated. Seeond  Edition.  Cloth,  2.00 

ee  pages  14  and  15  for  list  of  ?  Quiz-Compends  f 


12        STUDENTS'  TEXT-BOOKS  AND  MANUALS. 

PRACTICE. 

Taylor.  Practice  of  Medicine.  A  Manual.  By  Frederick 
Taylor,  M.D.,  Physician  to,  and  Lecturer  on  Medicine  at,  Guy's 
Hospital,  London  ;  Physician  to  Evelina  Hospital  for  Sick  Chil- 
dren, and  Examiner  in  Materia  Medica  and  Pharmaceutical 
Chemistry,  University  of  London.  Cloth,  4.00 

Roberts'  Practice.  New  Revised  Edition.  A  Handbook 
of  the  Theory  and  Practice  of  Medicine.  By  Frederick  T. 
Roberts,  M.D.  ;  M.R.C.P.,  Professor  of  Clinical  Medicine  and 
Therapeutics  in  University  College  Hospital,  London.  Seventh 
Edition.  Octavo.  Cloth,  5.50 ;  Sheep,  6.50 

Hughes.  Compend  of  the  Practice  of  Medicine.  4th  Edi- 
tion. Two  parts,  each,  Cloth,  i.oo;  Interleaved  for  Notes,  1.25 
PART  i. — Continued,  Eruptive  and  Periodical  Fevers,  Diseases 

of  the  Stomach,  Intestines,  Peritoneum,  Biliary  Passages,  Liver, 

Kidneys,  etc.,  and  General  Diseases,  etc. 

PART   n.— Diseases   of  the   Respiratory    System,   Circulatory 

System  and  Nervous  System ;  Diseases  of  the  Blood,  etc. 

.  Physician's  Edition.    Fourth  Edition.    Including  a  Section 
on  Skin  Diseases.  With  Index,    i  vol.   Full  Morocco,  Gilt,  2.50 

From  John  A.  Robinson,  M.D.,  Assistant  to   Chair  of  Clinical 
Medicine t  now  Lecturer  on  Materia  Medica,  Rusk  Medical  Col- 
lege, Chicago. 
"  Meets  with   my  hearty  approbation   as   a   substitute  for  the 

ordinary  note  books  almost  universally  used  by  medical  students. 

It  is  concise,  accurate,  well  arranged  and  lucid,     .     .     .    just  the 

thing  for  students  to  use  while  studying  physical  diagnosis  and  the 

more  practical  departments  of  medicine. 

PRESCRIPTION   BOOKS. 

Wythe's  Dose  and  Symptom  Book.  Containing  the  Doses 
and  Uses  of  all  the  principal  Articles  of  the  Materia  Medica,  etc. 
Seventeenth  Edition.  Completely  Revised  and  Rewritten.  Just, 
Ready.  32mo.  Cloth,  i.oo;  Pocket-book  style,  1.25 

Pereira's  Physician's  Prescription  Book.  Containing  Lists 
of  Terms,  Phrases,  Contractions  and  Abbreviations  used  in 
Prescriptions  Explanatory  Notes,  Grammatical  Construction  of 
Prescriptions,  etc.,  etc.  By  Professor  Jonathan  Pereira,  M.D. 
Sixteenth  Edition.  32mo.  Cloth,  i.oo;  Pocket-book  style,  1.25 

PHARMACY. 

Stewart's  Compend  of  Pharmacy.  Based  upon  Remington's 
Text-Book  of  Pharmacy.  Third  Edition,  Revised.  With  new 
Tables,  Index,  Etc.  Cloth,  i.oo;  Interleaved  for  Notes,  1.25 

Robinson.  Latin  Grammar  of  Pharmacy  and  Medicine. 
By  H.  D.  Robinson,  PH.D.,  Professor  of  Latin  Language  and 
Literature,  University  of  Kansas,  Lawrence.  With  an  Intro- 
duction by  L.  E.  Sayre,  PH.G.,  Professor  of  Pharmacy  in,  and 
Dean  of,  the  Dept.  of  Pharmacy,  University  of  Kansas.  i2mo. 

Cloth,  2.00 

SKIN  DISEASES. 

Anderson,  (McCall)  Skin  Diseases.  A  complete  Text-Book, 
with  Colored  Plates  and  numerous  Wood  Engravings.  8vo. 

Cloth,  4.50;  Leather,  5.50 
>&S~  See  pages  2  to  3  for  list  of  New  Manuals. 


STUDENTS'   TEXT-BOOKS  AND  MANUALS.        13- 


Skin  Diseases  : — Continued. 

Van  Harlingen  on  Skin  Diseases.  A  Handbook  of  the  Dis- 
eases of  the  Skin,  their  Diagnosis  and  Treatment  (arranged  alpha- 
betically). By  Arthur  Van  Harlingen,  M.D.,  Clinical  Lecturer 
on  Dermatology,  Jefferson  Medical  College ;  Prof,  of  Diseases  of 
the  Skin  in  the  Philadelphia  Polyclinic.  ad  Edition.  Enlarged. 
With  colored  and  other  plates  and  illustrations.  lamo.  Cloth,  2.50 

Bulkley.  The  Skin  in  Health  and  Disease.  By  L.  Duncan 
Bulkley,  Physician  to  the  N.  Y.  Hospital.  Illus.  Cloth,  .50 

SURGERY   AND    BANDAGING. 

Jacobson.  Operations  in  Surgery.  A  Systematic  Handbook 
for  Physicians,  Students  and  Hospital  Surgeons.  By  W.  H.  A. 
Jacobson,  B.A.,  Oxon.  F.R.C.S.  Eng. ;  Ass't  Surgeon  Guy's  Hos- 
pital ;  Surgeon  at  Royal  Hospital  for  Children  and  Women,  etc. 
199  Illustrations.  1006  pages.  8vo.  Cloth.  5.00;  Leather,  6.00 
Heath's  Minor  Surgery,  and  Bandaging.  Ninth  Edition.  142 
Illustrations.  60  Formulae  and  Diet  Lists.  Cloth,  2.00 

Horwitz's    Compend    of    Surgery,    Minor    Surgery    and1 
Bandaging,    Amputations,    Fractures,    Dislocations,   Surgical 
Diseases,  and  the  Latest  Antiseptic  Rules,  etc.,  with  Differential 
Diagnosis  and  Treatment.     By  ORVILLE  HOKWITZ,  B.S.,  M.D., 
Demonstrator  of  Surgery,  Jefferson  Medical  College.    4th  edition. 
Enlarged  and  Rearranged.     136   Illustrations  and   84  Formulae. 
121110.        Cloth,  i.oo;  Interleaved  for  the  addition  of  Notes,  1.25 
*#*The  new  Section  on  Bandaging  and  Surgical  Dressings,  con- 
sists  of  32  Pages  and  41   Illustrations.     Every  Bandage  of  any 
importance   is   figured.      This,  with    the  Section   on  Ligation  of 
Arteries,  forms  an  ample  Text-book  for  the  Surgical  Laboratory. 
Walsham.    Manual  of  Practical  Surgery.     For  Students  and 
Physicians.     By  WM.  J.  WALSHAM,  M.D.,  F.R.C.S.,  Asst.  Surg. 
to,  and  Dem.  of  Practical  Surg.  in,  St.  Bartholomew's  Hospital, 
Surgeon  to   Metropolitan   Free   Hospital,    London.      With  236 
Engravings.     See  Page  2.  Cloth,  3.00;  Leather,  3.50 

URINE,  URINARY   ORGANS,  ETC. 

Holland.  The  Urine,  and  Common  Poisons  and  The 
Milk.  Chemical  and  Microscopical,  for  Laboratory  Use.  Illus- 
trated. Third  Edition.  i2mo.  Interleaved.  Cloth,  i.oo 

Ralfe.  Kidney  Diseases  and  Urinary  Derangements.  42  Illus- 
trations. i2mo.  572  pages.  Cloth,  2.75 

Marshall  and  Smith.  On  the  Urine.  The  Chemical  Analysis  of 
the  Urine.  By  John  Marshall,  M.D.,  Chemical  Laboratory,  Univ. 
of  Penna;  and  Prof.  E.  F.  Smith,  PH.D.  Col.  Plates.  Cloth,  i.oo 

Thompson.  Diseases  of  the  Urinary  Organs.  Eighth 
London  Edition.  Illustrated.  Cloth,  3.50 

Tyson.  On  the  Urine.  A  Practical  Guide  to  the  Examination 
of  Urine.  With  Colored  Plates  and  Wood  Engravings.  6th  Ed. 
Enlarged.  i2mo.  Cloth,  1.50 

Van  Niiys,  Urine  Analysis.    Illus.  Cloth,  2.00 

VENEREAL  DISEASES. 

Hill  and  Cooper.  Student's  Manual  of  Venereal  Diseases, 
with  Formulae.  Fourth  Edition.  i2mo.  Cloth, 'i.oo 

ee  pages  14.  and  15  for  list  of  .'  Quiz-Contpends  f 


NEW  AND  REVISED  EDITIONS. 

PQUIZ-COMPENDS? 

The  Best  Compends  for  Students'  Use 
in  the  Quiz  Class,  and  when  Pre- 
paring for  Examinations. 

Compiled  in  accordance  with  the  latest  teachings  of  promi- 
nent lecturers  and  the  most  popular  Text-books. 
They  form  a  most  complete,  practical  and  exhaustive 
set  of  manuals,  containing  information  nowhere  else  col- 
lected in  such  a  condensed,  practical  shape.  Thoroughly 
up  to  the  times  in  every  respect,  containing  many  new 
prescriptions  and  formulae,  and  over  two  hundred  and 
fifty  illustrations,  many  of  which  have  been  drawn  and 
engraved  specially  for  this  series.  The  authors  have  had 
large  experience  as  quiz-masters  and  attaches  of  colleges, 
with  exceptional  opportunities  for  noting  the  most  recent 
advances  and  methods. 

Cloth,  each  $1.00.     Interleaved  for  Notes,  $1.25. 
No.  i.    HUMAN  ANATOMY,  "  Based  upon  Gray."    Fifth 
Enlarged  Edition,  including  Visceral  Anatomy,  formerly 
published    separately.      16     Lithograph     Plates,     New 
Tables  and   117  other  Illustrations.      By  SAMUEL  O.  L. 
POTTER,  M.A.,  M.D.,  late  A.  A.  Surgeon  U.  S.  Army.     Professor 
of  Practice,  Cooper  Medical  College,  San  Francisco. 
Nos.  2  and  3.     PRACTICE  OF  MEDICINE.     Fourth  Edi- 
tion.    By  DANIEL  E.  HUGHES,  M.D.,  Demonstrator  of  Clinical 
Medicine  in  Jefferson  Medical  College,  Philadelphia.  In  two  parts. 
PART  I. — Continued,  Eruptive  and  Periodical  Fevers,  Diseases 
of  the  Stomach,  Intestines,  Peritoneum,  Biliary  Passages,  Liver, 
Kidneys,  etc.  (including  Tests  for  Urine),  General  Diseases,  etc. 

PART  II. — Diseases  of  the  Respiratory  System  (including  Phy- 
sical Diagnosis),  Circulatory  System  and  Nervous  System;  Dis- 
eases of  the  Blood,  etc. 

***  These  little  books  can  be  regarded  as  a  full  set  of  notes  upon 
the  Practice  of  Medicine,  containing  the  Synonyms,  Definitions, 
Causes,  Symptoms,  Prognosis,  Diagnosis,  Treatment,  etc.,  of  each 
disease,  and  including  a  number  of  prescriptions  hitherto  unpub- 
lished. 

No.  4.  PHYSIOLOGY,  including  Embryology.  Fifth 
Edition.  By  ALBERT  P.  BRUBAKER,  M.D.,  Prof,  of  Physiology, 
Penn'a  College  of  Dental  Surgery  ;  Demonstrator  of  Physiology 
in  Jefferson  Medical  College,  Philadelphia.  Revised,  Enlarged 
and  Illustrated. 

No.  5.  OBSTETRICS.  Illustrated.  Fourth  Edition.  By 
HENRY  G.  LANDIS,  M.D.,  Prof,  of  Obstetrics  and  Diseases  of 
Women,  in  Starling  Medical  College,  Columbus,  O.  Revised 
E'dition.  New  Illustrations. 


BLAKISTON'S  ?  QUIZ-COMPENDS  ? 

No.  6.  MATERIA  MEDICA,  THERAPEUTICS  AND 
PRESCRIPTION  WRITING.  Fifth  Revised  Edition. 

With  especial  Reference  to  the  Physiological  Action  of  Drugs, 
and  a  complete  article  on  Prescription  Writing.  Based  on  the 
Last  Revision  of  the  U.  S.  Pharmacopoeia,  and  including  many 
unofficinal  remedies.  By  SAMUEL  O.  L.  POTTER,  M.A.,  M.D., 
late  A.  A.  Surg.  U.  S.  Army ;  Prof,  of  Practice,  Cooper  Medical 
College,  San  Francisco.  Improved  and  Enlarged,  with  Index. 

No.  7.  GYNAECOLOGY.  A  Compend  of  Diseases  of  Women. 
By  HENRY  MORRIS,  M.D.,  Demonstrator  of  Obstetrics,  Jefferson 
Medical  College,  Philadelphia.  Illustrated. 

No.  8.  DISEASES  OF  THE  EYE  AND  REFRACTION, 
including  Treatment  and  Surgery.  By  L.  WEBSTER  Fox,  M.D., 
Chief  Clinical  Assistant  Ophthalmological  Dept.,  Jefferson  Med- 
ical College,  etc.,  and  GEO.  M.  GOULD,  M.D.  71  Illustrations,  39 
Formulse.  Second  Enlarged  and  Improved  Edition.  Index. 

No.  9.  SURGERY,  Minor  Surgery  and  Bandaging.  Illus- 
trated. Fourth  Edition.  Including  Fractures,  Wounds, 
Dislocations,  Sprains,  Amputations  and  other  operations  ;  Inflam- 
mation, Suppuration,  Ulcers,  Syphilis,  Tumors,  Shock,  etc. 
Diseases  of  the  Spine,  Ear,  Bladder,  Testicles,  Anus,  and 
other  Surgical  Diseases.  By  ORVILLE  HORWITZ,  A.M.,  M.D., 
Demonstrator  of  Surgery,  Jefferson  Medical  College.  Revised 
and  Enlarged.  84  Formulae  and  136  Illustrations. 

No.  10.  CHEMISTRY.  Inorganic  and  Organic.  For  Medical 
and  Dental  Students.  Including  Urinary  Analysis  and  Medical 
Chemistry.  By  HENRY  LEFFMANN,  M.D.,  Prof,  of  Chemistry  in 
Penn'a  College  of  Dental  Surgery,  Phila.  Third  Edition,  Revised 
and  Rewritten,  with  Index. 

No.  ii.  PHARMACY.  Based  upon  "  Remington's  Text-book 
of  Pharmacy."  By  F.  E.  STEWART,  M.D.,  PH. G.,  Quiz-Master 
at  Philadelphia  College  of  Pharmacy.  Third  Edition,  Revised. 

No.  12.  VETERINARY  ANATOMY  AND  PHYSIOL- 
OGY. 29  Illustrations.  By  WM.  R.  BALLOU,  M.D.,  Prof,  of 
Equine  Anatomy  at  N.  Y.  College  of  Veterinary  Surgeons. 

No.  13.  DENTAL  PATHOLOGY  AND  DENTAL  MEDI- 
CINE. Containing  all  the  most  noteworthy  points  of  interest 
to  the  Dental  student.  By  GEO.  W.  WARREN,  D.D.S.,  Clinical 
Chief,  Penn'a  College  of  Dental  Surgery,  Philadelphia.  Illus. 

No.  14.  DISEASES  OF  CHILDREN.  By  DR.  MARCUS  P. 
HATFIELD,  Prof,  of  Diseases  of  Children,  Chicago  Medical 
College.  Illustrated. 

Bound  in  Cloth,  $1.    Interleaved,  for  the  Addition  of  Notes,  $1.25. 


These  books  are  constantly  revised  to  keep  up  with 
the  latest  teachings  and  discoveries,  so  that  they  contain 
all  the  new  methods  and  principles.  No  series  of  books 
are  so  complete  in  detail,  concise  in  language,  or  so  well 
printed  and  bound.  Each  one  forms  a  complete  set  of 
notes  ^lpon  the  subject  under  consideration. 

Illustrated  Descriptive  Circular  Free. 


JUST  PUBLISHED. 


GOULD'S  NEW 

MEDICAL  DICTIONARY 


COMPACT. 

CONCISE. 
PRACTICAL 
ACCURATE. 

COMPREHENSIVE 
UP  TO  DATE. 


It  contains  Tables  of  the  Arteries,  Bacilli,  Gan- 
glia,    Leucomaines,    Micrococci,    Muscles, 
Nerves,    Plexuses,     Ptomaines,    etc., 
etc.,  that  will  be  found  of  great 
use   to   the    student. 


Small  octavo,  520  pages,  Half-Dark  Leather,      .     $3.25 
With  Thumb  Index,  Half  Morocco,  marbled  edges,  4.25 


From  J.  M.  DACOSTA,  M.  D.,  Professor  of  Practice  and 
Clinical  Medicine,  Jefferson  Medical  College,  Philadelphia. 

"I find  it  an  excellent  -work,  doing  credit  to  tne  learning  and 
discrimination  of  the  author." 


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